We are the wild!

.project

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <projectDescription>
-	<name>lab5-test</name>
+	<name>lab5-lab5-itmo</name>
 	<comment>Project lab5-test created by Buildship.</comment>
 	<projects>
 	</projects>

.settings/org.eclipse.buildship.core.prefs

@@ -1,2 +1,13 @@
-connection.project.dir=app
+arguments=--init-script /home/oxff/.cache/jdtls/config/org.eclipse.osgi/58/0/.cp/gradle/init/init.gradle
+auto.sync=false
+build.scans.enabled=false
+connection.gradle.distribution=GRADLE_DISTRIBUTION(WRAPPER)
+connection.project.dir=
 eclipse.preferences.version=1
+gradle.user.home=
+java.home=/usr/lib/jvm/java-21-openjdk
+jvm.arguments=
+offline.mode=false
+override.workspace.settings=true
+show.console.view=true
+show.executions.view=true

app/.classpath

@@ -12,6 +12,13 @@
 			<attribute name="gradle_used_by_scope" value="main,test"/>
 		</attributes>
 	</classpathentry>
+	<classpathentry kind="src" output="bin/test" path="src/test/java">
+		<attributes>
+			<attribute name="gradle_scope" value="test"/>
+			<attribute name="gradle_used_by_scope" value="test"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-21/"/>
 	<classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
 	<classpathentry kind="output" path="bin/default"/>

app/.settings/org.eclipse.buildship.core.prefs

@@ -1,13 +1,13 @@
-arguments=--init-script /home/oxff/.cache/jdtls/config/org.eclipse.osgi/58/0/.cp/gradle/init/init.gradle
+arguments=
 auto.sync=false
 build.scans.enabled=false
-connection.gradle.distribution=GRADLE_DISTRIBUTION(LOCAL_INSTALLATION(/usr/share/java/gradle))
+connection.gradle.distribution=GRADLE_DISTRIBUTION(WRAPPER)
-connection.project.dir=
+connection.project.dir=..
 eclipse.preferences.version=1
 gradle.user.home=
-java.home=/usr/lib/jvm/java-21-openjdk
+java.home=
 jvm.arguments=
 offline.mode=false
-override.workspace.settings=true
+override.workspace.settings=false
-show.console.view=true
+show.console.view=false
-show.executions.view=true
+show.executions.view=false

app/src/main/java/itmo/lab5/App.java

@@ -19,9 +19,19 @@ import itmo.lab5.models.Flat;
 import itmo.lab5.parser.Reader;
 import itmo.lab5.cli.helpers.History;
 
+/**
+ * This class is an entry point of the application that manages a collection of
+ * {@code Flat} objects.
+ * The main method creates REPL that provide ability create or modificate data
+ */
 public class App {
     private static final Logger LOGGER = Logger.getLogger(FileHandler.class.getName());
 
+    /**
+     * The main method that serves as the entry point for the application.
+     * 
+     * @param g_args command-line arguments (not used)
+     */
     public static void main(String[] g_args) {
         Path dataFilePath = null;
         var history = new History();
@@ -37,7 +47,6 @@ public class App {
                 .register("remove_key", new RemoveKeyCommand())
                 .register("history", new HistoryCommand())
                 .register("insert", new InsertCommand())
-                .register("update", new UpdateCommand())
                 .register("save", new SaveCommand())
                 .register("execute_script", new ExecuteCommand())
                 .register("print_field_ascending_number_of_rooms", new FieldCommand())
@@ -51,7 +60,7 @@ public class App {
             dataFilePath = getDataFileFromEnv("LAB5_DATA");
             flats = new Reader().parseCSV(dataFilePath.toFile());
         } catch (IllegalArgumentException | IOException e) {
-            LOGGER.log(Level.WARNING, "There's error while loading file: " + e.getMessage());
+            LOGGER.log(Level.WARNING, "There's error while loading file: {0}", e.getMessage());
             return;
         }
 
@@ -79,14 +88,22 @@ public class App {
         }
     }
 
+    /**
+     * Retrieves the path to the data file from the specified environment variable.
+     *
+     * @param envVariable the name of the environment variable that contains the
+     *                    file path
+     * @return the path to the data file
+     * @throws IOException              if an I/O error happens
+     * @throws IllegalArgumentException if the env variable is not set or invalid
+     */
     public static Path getDataFileFromEnv(String envVariable) throws IOException {
         String envPath = System.getenv(envVariable);
         final Path path;
 
-        if (envPath == null || envPath.trim().isEmpty()) {
+        if (envPath == null || envPath.trim().isEmpty())
             throw new IllegalArgumentException(
                     "Environment variable '" + envVariable + "' is not set or empty.");
-        }
 
         try {
             path = Paths.get(envPath);
@@ -97,18 +114,15 @@ public class App {
                     ex);
         }
 
-        if (!Files.exists(path)) {
+        if (!Files.exists(path))
             throw new IllegalArgumentException("The file at path '" + path + "' does not exist.");
-        }
 
-        if (!Files.isRegularFile(path)) {
+        if (!Files.isRegularFile(path))
             throw new IllegalArgumentException("The path '" + path + "' is not a file. Check twice!");
-        }
 
-        if (!Files.isReadable(path)) {
+        if (!Files.isReadable(path))
             throw new IllegalArgumentException("The file at path '" + path + "' is not readable. " +
                     "Check file permissions!");
-        }
 
         LOGGER.info("File '" + path + "' exists and is readable.");
         return path;

app/src/main/java/itmo/lab5/cli/CommandBuilder.java

@@ -2,18 +2,37 @@ package itmo.lab5.cli;
 
 import itmo.lab5.interfaces.Command;
 
+/**
+ * This class is responsible for constructing a CommandRegistry
+ * which contains all commands 
+ */
 public class CommandBuilder {
   private final CommandRegistry registry;
   
+  /**
+  * Constructs a new instance, initializing an empty CommandRegistry.
+  */
   public CommandBuilder() {
     this.registry = new CommandRegistry();
   }
 
+  /**
+  * Registers a new command with the specified name in the command registry.
+  *
+  * @param name the name of the command to register
+  * @param newCommand the command instance to be registered
+  * @return the current instance for method chaining
+  */
   public CommandBuilder register(String name, Command newCommand) {
     this.registry.register(name, newCommand);
     return this;
   }
   
+  /**
+  * Builds and returns the constructed CommandRegistry containing all registered commands.
+  *
+  * @return the constructed CommandRegistry
+  */
   public CommandRegistry build() {
     return this.registry;
   }

app/src/main/java/itmo/lab5/cli/CommandContext.java

@@ -2,13 +2,29 @@ package itmo.lab5.cli;
 
 import java.util.HashMap;
 
+/**
+ * This class provides a context for storing and retrieving key-value pairs 
+ */
 public class CommandContext {
   private HashMap<String, Object> data = new HashMap<>();
 
+  /**
+   * Stores a value associated with the specified key in the context.
+   *
+   * @param key the key under which the value is to be stored
+   * @param value the value to be stored in the context
+   */
   public void set(String key, Object value) {
     this.data.put(key, value);
   }
   
+  /**
+    * Retrieves the value associated with the specified key from the context.
+    *
+    * @param name the key associated with value
+    * @return the value associated with the specified key, or {@code null}
+    * if the key does not exist
+    */
   public Object get(String name) {
     return this.data.get(name);
   }

app/src/main/java/itmo/lab5/cli/CommandInvoker.java

@@ -3,17 +3,37 @@ package itmo.lab5.cli;
 import itmo.lab5.cli.helpers.History;
 import itmo.lab5.interfaces.*;
 
+/**
+ * Invokes commands from a command registry and maintains command history.
+ */
 public class CommandInvoker {
+  
   private final CommandRegistry registry;
   private final CommandContext context;
   private final History history;
 
+  /**
+   * Constructs a CommandInvoker with the specified command registry,
+   * context, and history.
+   *
+   * @param registry the command registry to retrieve commands from.
+   * @param context the context to be passed to commands during execution.
+   * @param history the history object to track executed commands.
+   */
   public CommandInvoker(CommandRegistry registry, CommandContext context, History history) {
     this.registry = registry;
     this.context = context;
     this.history = history;
   }
 
+  /**
+   * Executes a command by its name with the provided arguments.
+   *
+   * @param commandName the name of the command to execute.
+   * @param args an array of arguments to pass to the command.
+   * @return the result of the command execution, or an error message if
+   *         the command is unknown or an exception occurs during execution.
+   */
   public String executeCommand(String commandName, String[] args) {
     Command command = registry.getByName(commandName);
     if (command != null) {

app/src/main/java/itmo/lab5/cli/CommandRegistry.java

@@ -4,17 +4,40 @@ import java.util.HashMap;
 import java.util.Map;
 import itmo.lab5.interfaces.Command;
 
+/**
+ * Manages the registration and retrieval of commands.
+ */
 public class CommandRegistry {
+  
   private final Map<String, Command> commands = new HashMap<>();
 
+  /**
+   * Registers a new command with the specified name.
+   *
+   * @param name the name of the command to register.
+   * @param newCommand the command instance to register.
+   */
   public void register(String name, Command newCommand) {
     this.commands.put(name, newCommand);
   }
 
+  /**
+   * Retrieves a command by its name.
+   *
+   * @param name the name of the command to retrieve.
+   * @return the command associated with the specified name, or null
+   *         if no command is found.
+   */
   public Command getByName(String name) {
     return this.commands.get(name);
   }
 
+  /**
+   * Returns a map of all registered commands.
+   *
+   * @return a map where the keys are command names and the values are
+   *         the corresponding command instances.
+   */
   public Map<String, Command> getAllCommands() {
     return this.commands;
   }

app/src/main/java/itmo/lab5/cli/commands/ClearCommand.java

@@ -6,18 +6,34 @@ import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.models.Flat;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to clear the collection of Flat objects.
+ * 
+ * When executed, this command retrieves the collection from the command context 
+ * and removes all items from it, effectively emptying the collection.
+ */
 public class ClearCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    var collection = new HashMap<Integer, Flat>();
     
-    try {
+    /**
-      collection = (HashMap<Integer, Flat>) context.get("collection");
+     * Executes the clear command, removing all items from the collection 
-    } catch (ClassCastException e) {
+     * of flats.
-      return "Can't clear collection. It might be missed";
+     *
+     * @param args an array of arguments passed to the command 
+     * @param context the command context that contains the collection of flats
+     * @return a message indicating the result of the operation, or an error message if the collection cannot be parsed
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        var collection = new HashMap<Integer, Flat>();
+
+        try {
+            collection = (HashMap<Integer, Flat>) context.get("collection");
+        } catch (ClassCastException e) {
+            return "Can't clear collection. It might be missed.";
+        }
+
+        collection.clear();
+        return "Collection was successfully cleared!";
     }
-
-    collection.clear();
-    return "Collection was successfuly cleared!";
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/ExecuteCommand.java

@@ -10,52 +10,68 @@ import itmo.lab5.cli.CommandInvoker;
 import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.*;
 
+/**
+ * This class implements the Command} interface and provides
+ * functionality to execute a script file containing a series of commands.
+ *
+ * When executed, this command reads commands from the specified script file and
+ * executes them sequentially. It also checks for recursive script execution 
+ * to prevent infinite loops.
+ */
 public class ExecuteCommand implements Command {
-  private static final Set<String> executingScripts = new HashSet<String>();
+    private static final Set<String> executingScripts = new HashSet<String>();
 
-  @Override
+    /**
-  public String execute(String args[], CommandContext context) {
+     * Executes the script command, running the commands specified in the given 
-    if (args.length < 1) {
+     * script file.
-      return "Usage: execute_script <file_name>";
+     *
-    }
+     * @param args an array of arguments passed to the command, where the first element is expected to be the name of the script file
-
+     * @param context the command context that contains the command invoker
-    String fileName = args[0];
+     * @return a string containing the output of the executed commands, or an error message if the script file cannot be found or executed
-    File scriptFile = new File(fileName);
+     */
-
+    @Override
-    if (executingScripts.contains(scriptFile.getAbsolutePath())) {
+    public String execute(String args[], CommandContext context) {
-      return "Error: Recursive script execution detected for file: " + fileName;
+        if (args.length < 1) {
-    }
+            return "Usage: execute_script <file_name>";
-
-    executingScripts.add(scriptFile.getAbsolutePath());
-
-    try (Scanner fileScanner = new Scanner(scriptFile)) {
-      CommandInvoker commandInvoker = (CommandInvoker) context.get("commandInvoker");
-      StringBuilder output = new StringBuilder();
-
-      while (fileScanner.hasNextLine()) {
-        String line = fileScanner.nextLine().trim();
-        if (line.isEmpty() || line.startsWith("#")) {
-          continue;
         }
 
-        try {
+        String fileName = args[0];
-          String[] parts = line.split(" ", 2);
+        File scriptFile = new File(fileName);
-          String commandName = parts[0];
-          String[] commandArgs = parts.length > 1 ? parts[1].split(" ") : new String[0];
 
-          String result = commandInvoker.executeCommand(commandName, commandArgs);
+        if (executingScripts.contains(scriptFile.getAbsolutePath())) {
-          output.append("> ").append(line).append("\n").append(result).append("\n");
+            return "Error: Recursive script execution detected for file: " + fileName;
-        } catch (Exception e) {
-          output.append("Error executing command '").append(line).append("': ")
-              .append(e.getMessage()).append("\n");
         }
-      }
 
-      return output.toString();
+        executingScripts.add(scriptFile.getAbsolutePath());
-    } catch (FileNotFoundException e) {
+
-      return "Error: Script file not found: " + fileName;
+        try (Scanner fileScanner = new Scanner(scriptFile)) {
-    } finally {
+            CommandInvoker commandInvoker = (CommandInvoker) context.get("commandInvoker");
-      executingScripts.remove(scriptFile.getAbsolutePath());
+            StringBuilder output = new StringBuilder();
+
+            while (fileScanner.hasNextLine()) {
+                String line = fileScanner.nextLine().trim();
+                if (line.isEmpty() || line.startsWith("#")) {
+                    continue;
+                }
+
+                try {
+                    String[] parts = line.split(" ", 2);
+                    String commandName = parts[0];
+                    String[] commandArgs = parts.length > 1 ? parts[1].split(" ") : new String[0];
+
+                    String result = commandInvoker.executeCommand(commandName, commandArgs);
+                    output.append("> ").append(line).append("\n").append(result).append("\n");
+                } catch (Exception e) {
+                    output.append("Error executing command '").append(line).append("': ")
+                        .append(e.getMessage()).append("\n");
+                }
+            }
+
+            return output.toString();
+        } catch (FileNotFoundException e) {
+            return "Error: Script file not found: " + fileName;
+        } finally {
+            executingScripts.remove(scriptFile.getAbsolutePath());
+        }
     }
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/ExitCommand.java

@@ -3,10 +3,24 @@ package itmo.lab5.cli.commands;
 import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.Command;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to terminate the application.
+ *
+ * When called, main loop will immediately stop.
+ */
 public class ExitCommand implements Command {
-  @Override
+    
-  public String execute(String[] args, CommandContext context) {
+    /**
-    System.exit(0);
+     * Executes the exit command, terminating the application.
-    return "";
+     *
-  }
+     * @param args an array of arguments passed to the command
+     * @param context the command context that may contain additional data
+     * @return an empty string
+     */
+    @Override
+    public String execute(String[] args, CommandContext context) {
+        System.exit(0);
+        return "";
+    }
 }

app/src/main/java/itmo/lab5/cli/commands/FieldCommand.java

@@ -7,7 +7,25 @@ import itmo.lab5.models.Flat;
 import java.util.*;
 import java.util.stream.Collectors;
 
+/**
+ * This class represents a command that processes a collection of Flat objects.
+ * This command sorts the flats by the number of rooms and prints the sorted 
+ * entries.
+ * 
+ * Implements the Command interface.
+ */
 public class FieldCommand implements Command {
+  
+  /**
+   * Executes the command, sorting and displaying the flats from the provided 
+   * collection.
+   *
+   * @param args an array of arguments passed to the command.
+   * @param context the context containing the collection of flats to be processed.
+   * @return a message indicating the result of the execution. If the collection is empty,
+   *         it returns "Nothing to show!". If the collection cannot be parsed, it returns
+   *         "Can't parse collection!".
+   */
   @Override
   public String execute(String args[], CommandContext context) {
     var collection = new HashMap<Integer, Flat>();
@@ -18,18 +36,17 @@ public class FieldCommand implements Command {
       return "Can't parse collection!";
     }
 
-    if (collection.isEmpty() || collection.size() == 0) {
+    if (collection.isEmpty()) {
       return "Nothing to show!";
     }
 
-    List<Map.Entry<Integer, Flat>> sortedEntries = collection.entrySet().stream()
+    var sortedEntries = collection.entrySet().stream()
         .sorted(Comparator.comparingInt(entry -> entry.getValue().getNumberOfRooms()))
         .collect(Collectors.toList());
 
-    sortedEntries.forEach(entry -> {
+    sortedEntries.forEach(entry ->
       System.out.println("Key: " + entry.getKey() +
-          ", Rooms: " + entry.getValue().getNumberOfRooms());
+          ", Rooms: " + entry.getValue().getNumberOfRooms()));
-    });
 
     return "";
   }

app/src/main/java/itmo/lab5/cli/commands/FilterCommand.java

@@ -8,9 +8,38 @@ import java.util.HashMap;
 import java.util.stream.Collectors;
 import java.util.*;
 
+/**
+ * Represents a command that filters a collection of {@link Flat} objects
+ * based on a specified classificator and a threshold value.
+ * 
+ * Implements the Command interface.
+ */
 public class FilterCommand implements Command {
   private String classificator;
 
+  /**
+   * Constructs a FilterCommand with the specified classificator.
+   *
+   * @param classificator the type of filtering to apply ("less" or "greater").
+   */
+  public FilterCommand(String classificator) {
+    this.classificator = classificator;
+  }
+
+  /**
+   * Executes the command, filtering and displaying the flats from the
+   * provided collection based on the threshold value.
+   *
+   * @param args an array of arguments where the first element is the
+   *             threshold value for filtering.
+   * @param context the context containing the collection of flats to be
+   *                processed.
+   * @return a message indicating the result of the execution. If no
+   *         classificator is provided, it returns "There's no
+   *         classificator provided!". If the collection cannot be parsed,
+   *         it returns "Can't parse collection!". If the collection is
+   *         empty or the threshold is null, it returns "Nothing to show!".
+   */
   @Override
   public String execute(String args[], CommandContext context) {
     if (args.length < 1)
@@ -22,36 +51,32 @@ public class FilterCommand implements Command {
 
     try {
       collection = (HashMap<Integer, Flat>) context.get("collection");
-      threshold = Integer.parseInt(args[0]);
+      threshold = Integer.valueOf(args[0]);
     } catch (ClassCastException e) {
       return "Can't parse collection!";
     }
 
-    if (collection.isEmpty() || collection.size() == 0 || threshold == null) {
+    if (collection.isEmpty() || threshold == null)
       return "Nothing to show!";
-    }
 
     final int finalThreshold = threshold;
-    if (classificator == "less") {
+    if (classificator.equals("less")) {
       result = collection.values().stream()
-          .filter(flat -> flat.getView() != null && flat.getView().ordinal() < finalThreshold)
+          .filter(flat -> flat.getView() != null && 
+                          flat.getView().ordinal() < finalThreshold)
           .sorted(Comparator.comparingInt(flat -> flat.getView().ordinal()))
           .collect(Collectors.toList());
     } else {
       result = collection.values().stream()
-          .filter(flat -> flat.getView() != null && flat.getView().ordinal() > finalThreshold)
+          .filter(flat -> flat.getView() != null && 
+                          flat.getView().ordinal() > finalThreshold)
           .sorted(Comparator.comparingInt(flat -> flat.getView().ordinal()))
           .collect(Collectors.toList());
     }
 
-    result.forEach(entry -> {
+    result.forEach(entry -> System.out.println(entry));
-      System.out.println(entry);
-    });
 
     return "";
   }
-
-  public FilterCommand(String classificator) {
-    this.classificator = classificator;
-  }
 }
+

app/src/main/java/itmo/lab5/cli/commands/HelpCommand.java

@@ -4,25 +4,40 @@ import itmo.lab5.cli.CommandContext;
 import itmo.lab5.cli.CommandRegistry;
 import itmo.lab5.interfaces.Command;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to display a list of available commands in the application.
+ * 
+ * When executed, this command retrieves the command registry from the context 
+ * and constructs a string that lists all registered commands. 
+ * If no commands are available, it informs user.
+ */
 public class HelpCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    var registry = (CommandRegistry) context.get("registry");
-    StringBuilder result = new StringBuilder();
     
-    if (registry == null) {
+    /**
-      result.append("There aren't any avaliable commands!");
+     * Executes the help command, returning a list of available commands.
-      return result.toString();
+     *
+     * @param args an array of arguments passed to the command
+     * @param context the command context that contains the command registry
+     * @return a string listing all available commands, or a message indicating that no commands are available
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        var registry = (CommandRegistry) context.get("registry");
+        StringBuilder result = new StringBuilder();
+
+        if (null == registry) {
+            result.append("There aren't any available commands!");
+            return result.toString();
+        }
+
+        result.append("List of available commands: ");
+        registry.getAllCommands().keySet().forEach(command -> 
+                result.append(command).append(", "));
+
+        return result
+            .delete(result.length() - 2, result.length())
+            .append(".")
+            .toString();
     }
-
-    result.append("List of avaliable commands: ");
-    for (String command : registry.getAllCommands().keySet()) {
-      result.append(command + ", ");
-    }
-
-    return result
-        .delete(result.length() - 2, result.length())
-        .append(".")
-        .toString();
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/HistoryCommand.java

@@ -4,20 +4,37 @@ import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.cli.helpers.*;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to display the command history of the application.
+ * 
+ * When executed, this command retrieves the history from the command context 
+ * and returns a string representation of the command history. If the history is 
+ * null or cannot be parsed, an appropriate error message is returned.
+ *
+ */
 public class HistoryCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    var history = new History();
     
-    try {
+    /**
-      history = (History) context.get("history");
+     * Executes the history command, returning latest 8 (by design).
-    } catch (ClassCastException e) {
+     *
-      return "There's problem with history. It might be null :(";
+     * @param args an array of arguments passed to the command
+     * @param context the command context that contains the history of commands
+     * @return a string representation of the command history, or an error message if the history cannot be parsed
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        var history = new History();
+
+        try {
+            history = (History) context.get("history");
+        } catch (ClassCastException e) {
+            return "There's a problem with history. It might be null :(";
+        }
+
+        if (null == history)
+            return "We reach the end of history. Somewhere in the world, one Fukuyama is rejoicing :_)";
+
+        return history.toString();
     }
-
-    if (history == null)
-      return "We reach End of History. Somewhere in the world, one Fukuyama is rejoicing :_)";
-
-    return history.toString();
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/InfoCommand.java

@@ -5,26 +5,40 @@ import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.models.Flat;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to display information about the collection.
+ * 
+ * When executed, this command retrieves the collection from the command context 
+ * and returns details about the collection, including its type, the type of its 
+ * items, and the number of items.
+ */
 public class InfoCommand implements Command {
-  @Override
+    /**
-  public String execute(String args[], CommandContext context) {
+     * Executes the info command, returning information about the collection of 
-    var flats = new HashMap<Integer, Flat>();
+     * flats.
+     *
+     * @param args an array of arguments passed to the command
+     * @param context the command context that contains the collection of flats
+     * @return a string containing information about the collection, or an error message if the collection cannot be parsed
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        var flats = new HashMap<Integer, Flat>();
 
-    try {
+        try {
-      flats = (HashMap<Integer, Flat>) context.get("collection");
+            flats = (HashMap<Integer, Flat>) context.get("collection");
-    } catch (ClassCastException e) {
+        } catch (ClassCastException e) {
-      return "Can't parse collection. Something goes wrong!";
+            return "Can't parse collection. Something goes wrong!";
+        }
+
+        if (null == flats || flats.isEmpty())
+            return "Collection is empty now!";
+
+        var anyFlat = flats.values().iterator().next();
+
+        return ("Collections stores in: Information about collection: " + flats.getClass().getName() + "\n" +
+                "Collection consists of: " + anyFlat.getClass().getName() + "\n" +
+                "Items: " + flats.size());
     }
-
-    if (flats == null || flats.isEmpty()) {
-      return "Collection is empty now!";
-    }
-
-    var anyFlat = flats.values().iterator().next();
-
-    return ("Information about collection: \n" +
-        "Collections stores in: " + flats.getClass().getName() + "\n" +
-        "Collection consists of: " + anyFlat.getClass().getName() + "\n" +
-        "Items: " + flats.size());
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/InsertCommand.java

@@ -1,10 +1,8 @@
 package itmo.lab5.cli.commands;
 
-import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Scanner;
-import java.util.function.Function;
 
 import itmo.lab5.cli.helpers.*;
 import itmo.lab5.cli.CommandContext;
@@ -12,84 +10,115 @@ import itmo.lab5.interfaces.Command;
 import itmo.lab5.models.enums.*;
 import itmo.lab5.models.*;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to insert a new Flat object into the collection.
+ * 
+ * This command can be executed in two modes: interactively, where the user is 
+ * prompted for input, or with command-line arguments, where parameters are 
+ * passed as key-value pairs. The command gathers all necessary information to 
+ * create a new flat and adds it to the collection.
+ * 
+ */
 public class InsertCommand implements Command {
-  private final Scanner scanner = new Scanner(System.in);
+    private final Scanner scanner = new Scanner(System.in);
-  private final ReaderUtil inputReader = new ReaderUtil(scanner);
+    private final ReaderUtil inputReader = new ReaderUtil(scanner);
 
-  @Override
+    /**
-  public String execute(String[] args, CommandContext context) {
+     * Executes the insert command, either interactively or with provided 
-    if (args.length == 0) {
+     * arguments.
-      return executeInteractive(context);
+     *
+     * @param args an array of arguments passed to the command; if empty, the command will execute interactively
+     * @param context the command context that contains the collection of flats
+     * @return a message indicating the result of the operation, or an error message if the collection cannot be parsed
+     */
+    @Override
+    public String execute(String[] args, CommandContext context) {
+        if (args.length == 0)
+            return executeInteractive(context);
+
+        return executeWithArgs(args, context);
     }
 
-    return executeWithArgs(args, context);
+    /**
-  }
+     * Executes the insert command interactively, prompting the user for input 
+     * to create a new flat.
+     *
+     * @param context the command context that contains the collection of flats
+     * @return a message indicating the result of the operation
+     */
+    private String executeInteractive(CommandContext context) {
+        Date creationDate = new Date();
+        String name = inputReader.promptString("- Enter name: ", false, null);
 
-  private String executeInteractive(CommandContext context) {
+        System.out.println("- Coordinates ");
-    Date creationDate = new Date();
+        int x = inputReader.promptNumber("\t Enter x: ", Integer.MIN_VALUE, Integer.MAX_VALUE, Integer::parseInt, null);
-    String name = inputReader.promptString("- Enter name: ", false, null);
+        Long y = inputReader.promptNumber("\t Enter y: ", Long.MIN_VALUE, Long.MAX_VALUE, Long::parseLong, null);
+        var coordinates = new Coordinates(x, y);
 
-    System.out.println("- Coordinates ");
+        Double area = inputReader.promptNumber("\t Enter square: ", 0.0, 626.0, Double::parseDouble, null);
-    int x = inputReader.promptNumber("\t Enter x: ", Integer.MIN_VALUE, Integer.MAX_VALUE, Integer::parseInt, null);
+        int numberOfRooms = inputReader.promptNumber("\t Enter rooms count: ", 1, Integer.MAX_VALUE, Integer::parseInt, null);
-    Long y = inputReader.promptNumber("\t Enter y: ", Long.MIN_VALUE, Long.MAX_VALUE, Long::parseLong, null);
-    var coordinates = new Coordinates(x, y);
 
-    Double area = inputReader.promptNumber("\t Enter square: ", 0.0, 626.0, Double::parseDouble, null);
+        System.out.println("- Furnish");
-    int numberOfRooms = inputReader.promptNumber("\t Enter rooms count: ", 1, Integer.MAX_VALUE, Integer::parseInt,
+        Furnish furnish = inputReader.promptEnum("\t Enter furnish type: ", Furnish.class, null);
-        null);
 
-    System.out.println("- Furnish");
+        System.out.println("- View");
-    Furnish furnish = inputReader.promptEnum("\t Enter furnish type: ", Furnish.class, null);
+        View view = inputReader.promptEnumNullable("\t Enter view type: ", View.class, null);
 
-    System.out.println("- View");
+        System.out.println("- Transport");
-    View view = inputReader.promptEnumNullable("\t Enter view type: ", View.class, null);
+        Transport transport = inputReader.promptEnum("\t Enter transport type: ", Transport.class, null);
 
-    System.out.println("- Transport");
+        System.out.println("- House");
-    Transport transport = inputReader.promptEnum("\t Enter transport type: ", Transport.class, null);
+        System.out.print("\t Enter house name: ");
+        String houseName = scanner.nextLine().trim();
 
-    System.out.println("- House");
+        House house = null;
-    System.out.print("\t Enter house name: ");
-    String houseName = scanner.nextLine().trim();
 
-    House house = null;
+        if (!houseName.isEmpty()) {
+            int year = inputReader.promptNumber("\t Enter house age: ", 1, 959, Integer::parseInt, null);
+            long floors = inputReader.promptNumber("\t Enter house floors count: ", 1L, 77L, Long::parseLong, null);
+            house = new House(houseName, year, floors);
+        }
 
-    if (!houseName.isEmpty()) {
+        try {
-      int year = inputReader.promptNumber("\t Enter house age: ", 1, 959, Integer::parseInt, null);
+            HashMap<Integer, Flat> collection = (HashMap<Integer, Flat>) context.get("collection");
-      long floors = inputReader.promptNumber("\t Enter house floors count: ", 1L, 77L, Long::parseLong, null);
+            int newID = collection.size() + 1;
-      house = new House(houseName, year, floors);
+            Flat flat = new Flat(
+                newID,
+                name,
+                coordinates,
+                creationDate,
+                area,
+                numberOfRooms,
+                furnish,
+                view,
+                transport,
+                house);
+
+            collection.put(newID, flat);
+        } catch (ClassCastException e) {
+            return "There's an error while trying to add new element. Collection is broken.";
+        }
+
+        return "New flat was successfully inserted!";
     }
 
-    try {
+    /**
-      HashMap<Integer, Flat> collection = (HashMap<Integer, Flat>) context.get("collection");
+     * Executes the insert command with provided arguments, creating a new flat 
-      int newID = collection.size() + 1;
+     * based on the key-value pairs.
-      Flat flat = new Flat(
+     *
-          newID,
+     * @param args an array of arguments passed to the command
-          name,
+     * @param context the command context that contains the collection of flats
-          coordinates,
+     * @return a message indicating the result of the operation
-          creationDate,
+     */
-          area,
-          numberOfRooms,
-          furnish,
-          view,
-          transport,
-          house);
-
-      collection.put(newID, flat);
-    } catch (ClassCastException e) {
-      return "There's an error while trying to add new element. Collection is broken.";
-    }
-
-    return "New flat was successfully inserted!";
-  }
-
   private String executeWithArgs(String[] args, CommandContext context) {
     HashMap<String, String> params = new HashMap<>();
 
     for (String arg : args) {
       String[] parts = arg.split("=", 2);
-      if (parts.length == 2) {
+
+      if (parts.length == 2)
         params.put(parts[0], parts[1]);
-      }
     }
 
     Date creationDate = new Date();
@@ -194,10 +223,10 @@ public class InsertCommand implements Command {
   public static <E extends Enum<E>> boolean isValidEnumValue(Class<E> enumClass, String value) {
     if (value == null)
       return false;
+
     for (E constant : enumClass.getEnumConstants()) {
-      if (constant.name().equals(value)) {
+      if (constant.name().equals(value))
         return true;
-      }
     }
     return false;
   }

app/src/main/java/itmo/lab5/cli/commands/RemoveKeyCommand.java

@@ -6,34 +6,51 @@ import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.models.Flat;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to remove a object from the collection based on its ID.
+ *
+ * When executed, this command retrieves the collection from the command 
+ * context, checks for the specified ID in the arguments, and removes 
+ * the corresponding object if it exists. If the ID is invalid
+ * or the collection is empty, appropriate error messages are returned.
+ */
 public class RemoveKeyCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    HashMap<Integer, Flat> flats = new HashMap<Integer, Flat>();
-    Integer idToDelete = null;
     
-    try {
+    /**
-      flats = (HashMap<Integer, Flat>) context.get("collection");
+     * Executes the remove key command, deleting a flat by ID.
-    } catch (ClassCastException e) {
+     *
-      return "There's a problem with collection parsing";
+     * @param args an array of arguments passed to the command, where the first element is expected to be the ID of the flat to remove
+     * @param context the command context that contains the collection of flats
+     * @return a message indicating the result of the operation, or an error message if the collection cannot be parsed or the ID is invalid
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        HashMap<Integer, Flat> flats = new HashMap<>();
+        Integer idToDelete = null;
+
+        try {
+            flats = (HashMap<Integer, Flat>) context.get("collection");
+        } catch (ClassCastException e) {
+            return "There's a problem with collection parsing.";
+        }
+
+        if (flats == null)
+            return "Collection is empty. Can't delete anything :(";
+
+        try {
+            idToDelete = Integer.valueOf(args[0]);
+        } catch (NumberFormatException e) {
+            return "You provided a mistyped argument!";
+        }
+
+        if (idToDelete < 0)
+            return "Check argument's value twice.";
+
+        if (!flats.containsKey(idToDelete))
+            return "Can't find flat with such ID.";
+
+        flats.remove(idToDelete);
+        return "Successfully deleted flat!";
     }
-
-    if (flats == null)
-      return "Collection is empty. Can't delete anything :(";
-
-    try {
-      idToDelete = Integer.parseInt(args[0]);
-    } catch (Exception e) {
-      return "You provide misstyped argument!";
-    }
-
-    if (idToDelete == null)
-      return "Check argument's value twice";
-
-    if (!flats.containsKey(idToDelete))
-      return "Can't find flat with such id";
-
-    flats.remove(idToDelete);
-    return "Successfuly deleted flat!";
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/ReplaceCommand.java

@@ -2,50 +2,223 @@ package itmo.lab5.cli.commands;
 
 import itmo.lab5.cli.CommandContext;
 import itmo.lab5.interfaces.*;
-import itmo.lab5.models.Flat;
+import itmo.lab5.models.*;
+import itmo.lab5.models.enums.*;
 
+import java.util.Date;
 import java.util.HashMap;
 
+/**
+ * Represents a command that replaces a flat in a collection based on a
+ * specified classificator ("greater" or "lower") and a given id.
+ * 
+ * Implements the {@link Command} interface.
+ */
 public class ReplaceCommand implements Command {
-  private String classificator;
   
+  private final String classificator;
+
+  /**
+   * Constructs a ReplaceCommand with the specified classificator.
+   *
+   * @param classificator the type of comparison for replacement, must be
+   *                      either "greater" or "lower".
+   * @throws IllegalArgumentException if the classificator is not valid.
+   */
   public ReplaceCommand(String classificator) {
-    this.classificator = classificator;
+    if (!classificator.equalsIgnoreCase("greater") && 
+        !classificator.equalsIgnoreCase("lower")) {
+      throw new IllegalArgumentException("Classificator must be either " +
+                                         "'greater' or 'lower'");
+    }
+    this.classificator = classificator.toLowerCase();
   }
 
+  /**
+   * Executes the command, replacing a flat in the collection if the
+   * specified condition is met.
+   *
+   * @param args an array of arguments where the first element is the id
+   *             of the flat to be replaced, followed by optional parameters
+   *             for the new flat.
+   * 
+   * @param context the context containing the collection of flats to be
+   *                processed.
+   * 
+   * @return a message indicating the result of the execution. If no
+   *         arguments are provided, it returns "No arguments provided.".
+   *         If the id format is invalid, it returns "Invalid id format.".
+   *         If the collection cannot be parsed, it returns "Collection is
+   *         corrupted or not found in context.". If the flat with the
+   *         specified id does not exist, it returns "No element with id
+   *         {id}". If the flat is successfully replaced, it returns a
+   *         success message; otherwise, it indicates that the condition
+   *         for replacement was not met.
+   */
   @Override
-  public String execute(String args[], CommandContext context) {
+  public String execute(String[] args, CommandContext context) {
-    var collection = new HashMap<Integer, Flat>();
+    if (args.length == 0)
-    int idToUpdate;
+      return "No arguments provided.";
 
+    int id;
+    try {
+      id = Integer.parseInt(args[0]);
+    } catch (NumberFormatException e) {
+      return "Invalid id format.";
+    }
+
+    HashMap<Integer, Flat> collection;
+    try {
+      collection = (HashMap<Integer, Flat>) context.get("collection");
+    } catch (ClassCastException e) {
+      return "Collection is corrupted or not found in context.";
+    }
+
+    if (!collection.containsKey(id))
+      return "No element with id " + id;
+
+    Flat oldFlat = collection.get(id);
+    Flat updatedFlat = buildFlatFromArgs(args, oldFlat);
+
+    if (updatedFlat == null)
+      return "Failed to create a new flat from arguments.";
+
+    int result = compareFlats(updatedFlat, oldFlat);
+    boolean shouldReplace = classificator.equals("greater") ? result > 0 : result < 0;
+
+    if (shouldReplace) {
+      collection.put(id, updatedFlat);
+      return "Flat with id " + id + " was replaced.";
+    } else {
+      return "Flat was not replaced: condition not met.";
+    }
+  }
+
+  /**
+   * Builds a new Flat object from the provided arguments, using the
+   * existing flat's properties as defaults.
+   *
+   * @param args an array of arguments containing the new flat's properties.
+   * @param oldFlat the existing flat to use as a reference for default values.
+   * @return a new Flat object or null if the creation fails.
+   */
+  private Flat buildFlatFromArgs(String[] args, Flat oldFlat) {
     HashMap<String, String> params = new HashMap<>();
-
     for (String arg : args) {
       String[] parts = arg.split("=", 2);
+
       if (parts.length == 2)
         params.put(parts[0], parts[1]);
     }
 
-    if (args.length < 1)
-      return "Can't get value without id!";
-
     try {
-      collection = (HashMap<Integer, Flat>) context.get("collection");
+      String name = params.getOrDefault("name", oldFlat.getName());
-    } catch (ClassCastException e) {
-      return "Can't parse collection!";
-    }
 
-    try {
+      Coordinates coordinates = oldFlat.getCoordinates();
-      idToUpdate = Integer.parseInt(args[0]);
+      if (params.containsKey("x") || params.containsKey("y")) {
+        int x = params.containsKey("x") ? Integer.parseInt(params.get("x")) : coordinates.getX();
+        long y = params.containsKey("y") ? Long.parseLong(params.get("y")) : coordinates.getY();
+        coordinates = new Coordinates(x, y);
+      }
+
+      Double area = params.containsKey("area") ? Double.parseDouble(params.get("area")) : oldFlat.getArea();
+      int numberOfRooms = params.containsKey("numberOfRooms") ? Integer.parseInt(params.get("numberOfRooms"))
+          : oldFlat.getNumberOfRooms();
+      Furnish furnish = params.containsKey("furnish") ? Furnish.valueOf(params.get("furnish").toUpperCase())
+          : oldFlat.getFurnish();
+      View view = params.containsKey("view") ? View.valueOf(params.get("view").toUpperCase()) : oldFlat.getView();
+      Transport transport = params.containsKey("transport") ? Transport.valueOf(params.get("transport").toUpperCase())
+          : oldFlat.getTransport();
+
+      House house = oldFlat.getHouse();
+      if (params.containsKey("name") || params.containsKey("year") || params.containsKey("floors")) {
+        String houseName = params.containsKey("name") ? params.get("name") : house.getName();
+        int year = params.containsKey("year") ? Integer.parseInt(params.get("year")) : house.getYear();
+        long floors = params.containsKey("houseFloors") ? Long.parseLong(params.get("houseFloors"))
+            : house.getNumberOfFloors();
+        house = new House(houseName, year, floors);
+      }
+
+      return new Flat(
+          oldFlat.getId(),
+          name,
+          coordinates,
+          new Date(),
+          area,
+          numberOfRooms,
+          furnish,
+          view,
+          transport,
+          house);
     } catch (NumberFormatException e) {
-      return "Can't parse provided id!";
+      return null;
+    }
+  }
+  
+  /**
+   * Compares two Flat objects based on various attributes such as area,
+   * number of rooms, furnish type, view, transport, and house details.
+   *
+   * @param f1 the first flat to compare.
+   * @param f2 the second flat to compare.
+   * @return a negative integer, zero, or a positive integer as the first
+   *         flat is less than, equal to, or greater than the second flat.
+   */
+  private int compareFlats(Flat f1, Flat f2) {
+    int result = safeCompare(f1.getArea(), f2.getArea());
+    if (result != 0)
+      return result;
+
+    result = Integer.compare(f1.getNumberOfRooms(), f2.getNumberOfRooms());
+    if (result != 0)
+      return result;
+
+    result = safeCompare(f1.getFurnish(), f2.getFurnish());
+    if (result != 0)
+      return result;
+
+    result = safeCompare(f1.getView(), f2.getView());
+    if (result != 0)
+      return result;
+
+    result = safeCompare(f1.getTransport(), f2.getTransport());
+    if (result != 0)
+      return result;
+
+    House h1 = f1.getHouse(), h2 = f2.getHouse();
+    if (h1 != null && h2 != null) {
+      result = Integer.compare(h1.getYear(), h2.getYear());
+      if (result != 0)
+        return result;
+
+      result = Long.compare(h1.getNumberOfFloors(), h2.getNumberOfFloors());
+      if (result != 0)
+        return result;
     }
 
-    if (collection.isEmpty() || collection.size() == 0)
+    return 0;
-      return "Nothing to show!";
+  }
 
-    var currentFlat = collection.get(idToUpdate);
+  /**
-
+   * Safely compares two comparable objects, handling null values.
-    return "";
+   *
+   * @param a the first object to compare.
+   * @param b the second object to compare.
+   * @param <T> the type of the objects being compared, which must extend
+   *            Comparable.
+   *
+   * @return a negative integer, zero, or a positive integer as the first
+   *         object is less than, equal to, or greater than the second
+   *         object. If both are null, returns 0; if one is null, the
+   *         other is considered greater.
+   */
+  private <T extends Comparable<T>> int safeCompare(T a, T b) {
+    if (a == null && b == null)
+      return 0;
+    if (a == null)
+      return -1;
+    if (b == null)
+      return 1;
+    return a.compareTo(b);
   }
 }

app/src/main/java/itmo/lab5/cli/commands/SaveCommand.java

@@ -3,71 +3,45 @@ package itmo.lab5.cli.commands;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.cli.*;
 import itmo.lab5.models.*;
-
+import itmo.lab5.parser.Writer;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
-import java.io.BufferedWriter;
 import java.util.HashMap;
-import java.text.SimpleDateFormat;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to save the current collection of Flat objects to a specified 
+ * file.
+ * 
+ * When executed, this command retrieves the collection and the file path from 
+ * the command context and uses a Writer instance to write the collection to the 
+ * specified file. If the collection or file path cannot be retrieved, an 
+ * appropriate error message is returned.
+ */
 public class SaveCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    var collection = new HashMap<Integer, Flat>();
-    String filePath = null;
     
-    try {
+    /**
-      collection = (HashMap<Integer, Flat>) context.get("collection");
+     * Executes the save command, saving the current collection of flats to a 
-      filePath = (String) context.get("path");
+     * file.
-    } catch (ClassCastException e) {
+     *
-      return "Can't parse collection!";
+     * @param args an array of arguments passed to the command (not used in this command)
-    }
+     * @param context the command context that contains the collection of flats and the file path
-
+     * @return a message indicating the result of the save operation, or an error message if the collection or file path cannot be parsed
-    if (filePath != null && collection != null) {
+     */
-      return saveCollectionToFile(collection, filePath);
+    @Override
-    } else {
+    public String execute(String args[], CommandContext context) {
-      return "Can't parse some object! Check filePath!";
+        var writer = new Writer();
-    }
+        var collection = new HashMap<Integer, Flat>();
-  }
+        String filePath = null;
-
-  static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
-
-  public String saveCollectionToFile(HashMap<Integer, Flat> flats, String filename) {
-    try (FileOutputStream fos = new FileOutputStream(filename);
-        OutputStreamWriter osw = new OutputStreamWriter(fos);
-        BufferedWriter writer = new BufferedWriter(osw)) {
-
-      for (Flat flat : flats.values()) {
-        String date = "";
 
         try {
-          date = dateFormat.format(flat.getCreationDate()).toString();
+            collection = (HashMap<Integer, Flat>) context.get("collection");
-        } catch (Exception e) {
+            filePath = (String) context.get("path");
-          System.out.println(e.getMessage());
+        } catch (ClassCastException e) {
+            return "Can't parse collection!";
         }
 
-        String line = String.format("%d,%s,%d,%d,%s,%.2f,%d,%s,%s,%s,%s,%d,%d\n",
+        if (filePath != null && collection != null)
-            flat.getId(),
+            return writer.writeCollection(filePath, collection);
-            flat.getName(),
+        else
-            flat.getCoordinates().getX(),
+            return "Can't parse some object! Check filePath!";
-            flat.getCoordinates().getY(),
-            date,
-            flat.getArea(),
-            flat.getNumberOfRooms(),
-            flat.getFurnish(),
-            flat.getView() != null ? flat.getView() : "",
-            flat.getTransport(),
-            flat.getHouse() != null ? flat.getHouse().getName() : "",
-            flat.getHouse() != null ? flat.getHouse().getYear() : 0,
-            flat.getHouse() != null ? flat.getHouse().getNumberOfFloors() : 0);
-        writer.write(line);
-      }
-
-      return "Collection has been saved to the file successfully.";
-    } catch (IOException e) {
-      e.printStackTrace();
-      return "An error occurred while saving the collection to file.";
     }
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/ShowCommand.java

@@ -6,25 +6,40 @@ import itmo.lab5.models.Flat;
 import itmo.lab5.interfaces.Command;
 import itmo.lab5.cli.CommandContext;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to display the contents of the collection of Flat objects.
+ * 
+ * When executed, this command retrieves the collection from the command context 
+ * and prints each Flat object to the standard output. If the collection is 
+ * empty, it returns a message indicating that there is nothing to show.
+ */
 public class ShowCommand implements Command {
-  @Override
-  public String execute(String args[], CommandContext context) {
-    var collection = new HashMap<Integer, Flat>();
     
-    try {
+    /**
-      collection = (HashMap<Integer, Flat>) context.get("collection");
+     * Executes the show command, displaying the contents of the collection
-    } catch (ClassCastException e) {
+     * of flats.
-      return "Can't parse collection!";
+     *
+     * @param args an array of arguments passed to the command
+     * @param context the command context that contains the collection of flats
+     * @return an empty string if the collection is displayed successfully, or an error message if the collection cannot be parsed
+     */
+    @Override
+    public String execute(String args[], CommandContext context) {
+        var collection = new HashMap<Integer, Flat>();
+
+        try {
+            collection = (HashMap<Integer, Flat>) context.get("collection");
+        } catch (ClassCastException e) {
+            return "Can't parse collection!";
+        }
+
+        if (collection.isEmpty())
+            return "Nothing to show!";
+
+        for (Flat flat : collection.values())
+            System.out.println(flat);
+
+        return "";
     }
-
-    if (collection.isEmpty() || collection.size() == 0) {
-      return "Nothing to show!";
-    }
-
-    for (Flat flat : collection.values()) {
-      System.out.println(flat);
-    }
-
-    return "";
-  }
 }

app/src/main/java/itmo/lab5/cli/commands/UpdateCommand.java

@@ -8,89 +8,105 @@ import itmo.lab5.interfaces.Command;
 import itmo.lab5.models.enums.*;
 import itmo.lab5.models.*;
 
+/**
+ * This class implements the Command interface and provides
+ * functionality to update an existing Flat object in the collection based on 
+ * its ID.
+ * 
+ * When executed, this command retrieves the flat with the specified ID from 
+ * the collection, prompts the user for new values to update the flat's 
+ * properties, and then saves the updated flat back to the collection.
+ * 
+ */
 public class UpdateCommand implements Command {
-  private final Scanner scanner = new Scanner(System.in);
+    private final Scanner scanner = new Scanner(System.in);
-  private final ReaderUtil inputReader = new ReaderUtil(scanner);
+    private final ReaderUtil inputReader = new ReaderUtil(scanner);
 
-  @Override
+    /**
-  public String execute(String[] args, CommandContext context) {
+     * Executes the update command, updating the flat with the specified ID.
-    if (args.length < 1) {
+     *
-      return "Usage: update id {element}";
+     * @param args an array of arguments passed to the command, where the first element is expected to be the ID of the flat to update
+     * @param context the command context that contains the collection of flats
+     * @return a message indicating the result of the operation, or an error message if the ID is invalid or the collection cannot be parsed
+     */
+    @Override
+    public String execute(String[] args, CommandContext context) {
+        if (args.length < 1)
+            return "Usage: update id {element}";
+
+        Map<Integer, Flat> collection = null;
+
+        int idToUpdate;
+        try {
+            idToUpdate = Integer.parseInt(args[0]);
+        } catch (NumberFormatException e) {
+            return "Invalid ID format.";
+        }
+
+        try {
+            collection = (Map<Integer, Flat>) context.get("collection");
+        } catch (ClassCastException e) {
+            return "There's an error while trying to parse collection.";
+        }
+
+        if (!collection.containsKey(idToUpdate))
+            return "No flat with ID: " + idToUpdate;
+
+        Flat oldFlat = collection.get(idToUpdate);
+
+        System.out.println("Updating flat with ID: " + idToUpdate);
+        String name = inputReader.promptString("- Enter name:", false, oldFlat.getName());
+
+        System.out.println("- Coordinates:");
+        int x = inputReader.promptNumber("\t Enter x:", Integer.MIN_VALUE, Integer.MAX_VALUE, Integer::parseInt,
+            oldFlat.getCoordinates().getX());
+        Long y = inputReader.promptNumber("\t Enter y:", Long.MIN_VALUE, Long.MAX_VALUE, Long::parseLong,
+            oldFlat.getCoordinates().getY());
+        Coordinates coordinates = new Coordinates(x, y);
+
+        Double area = inputReader.promptNumber("\t Enter square:", 0.0, 626.0, Double::parseDouble, oldFlat.getArea());
+        int rooms = inputReader.promptNumber("\t Enter rooms count:", 1, Integer.MAX_VALUE, Integer::parseInt,
+            oldFlat.getNumberOfRooms());
+
+        System.out.println("- Furnish:");
+        Furnish furnish = inputReader.promptEnum("\t Enter furnish type:", Furnish.class, oldFlat.getFurnish());
+
+        System.out.println("- View:");
+        View view = inputReader.promptEnumNullable("\t Enter view type:", View.class, oldFlat.getView());
+
+        System.out.println("- Transport:");
+        Transport transport = inputReader.promptEnum("\t Enter transport type:", Transport.class, oldFlat.getTransport());
+
+        System.out.println("- House:");
+        System.out.print("\t Enter house name: ");
+        String houseName = scanner.nextLine().trim();
+
+        House house = oldFlat.getHouse();
+        if (!houseName.isEmpty()) {
+            int year = inputReader.promptNumber("\t Enter house age: ", 1, 959, Integer::parseInt,
+                (house != null ? house.getYear() : 1));
+
+            long floors = inputReader.promptNumber("\t Enter house floors count: ", 1L, 77L, Long::parseLong,
+                (house != null ? house.getNumberOfFloors() : 1L));
+
+            house = new House(houseName, year, floors);
+        }
+
+        Date creationDate = new Date();
+
+        Flat updatedFlat = new Flat(
+            idToUpdate,
+            name,
+            coordinates,
+            creationDate,
+            area,
+            rooms,
+            furnish,
+            view,
+            transport,
+            house);
+
+        collection.put(idToUpdate, updatedFlat);
+        return "Flat with ID " + idToUpdate + " was successfully updated.";
     }
-
-    Map<Integer, Flat> collection = null;
-
-    int idToUpdate;
-    try {
-      idToUpdate = Integer.parseInt(args[0]);
-    } catch (NumberFormatException e) {
-      return "Invalid ID format.";
-    }
-
-    try {
-      collection = (Map<Integer, Flat>) context.get("collection");
-    } catch (ClassCastException e) {
-      return "There's an error while trying to parse collection";
-    }
-
-    if (!collection.containsKey(idToUpdate))
-      return "No flat with ID: " + idToUpdate;
-
-    Flat oldFlat = collection.get(idToUpdate);
-
-    System.out.println("Updating flat with ID: " + idToUpdate);
-    String name = inputReader.promptString("- Enter name:", false, oldFlat.getName());
-
-    System.out.println("- Coordinates:");
-    int x = inputReader.promptNumber("\t Enter x:", Integer.MIN_VALUE, Integer.MAX_VALUE, Integer::parseInt,
-        oldFlat.getCoordinates().getX());
-    Long y = inputReader.promptNumber("\t Enter y:", Long.MIN_VALUE, Long.MAX_VALUE, Long::parseLong,
-        oldFlat.getCoordinates().getY());
-    Coordinates coordinates = new Coordinates(x, y);
-
-    Double area = inputReader.promptNumber("\t Enter square:", 0.0, 626.0, Double::parseDouble, oldFlat.getArea());
-    int rooms = inputReader.promptNumber("\t Enter rooms count:", 1, Integer.MAX_VALUE, Integer::parseInt,
-        oldFlat.getNumberOfRooms());
-
-    System.out.println("- Furnish:");
-    Furnish furnish = inputReader.promptEnum("\t Enter furnish type:", Furnish.class, oldFlat.getFurnish());
-
-    System.out.println("- View:");
-    View view = inputReader.promptEnumNullable("\t Enter view type:", View.class, oldFlat.getView());
-
-    System.out.println("- Transport:");
-    Transport transport = inputReader.promptEnum("\t Enter transport type:", Transport.class, oldFlat.getTransport());
-
-    System.out.println("- House:");
-    System.out.print("\t Enter house name: ");
-    String houseName = scanner.nextLine().trim();
-
-    House house = oldFlat.getHouse();
-    if (!houseName.isEmpty()) {
-      int year = inputReader.promptNumber("\t Enter house age: ", 1, 959, Integer::parseInt,
-          (house != null ? house.getYear() : 1));
-
-      long floors = inputReader.promptNumber("\t Enter house floors count: ", 1L, 77L, Long::parseLong,
-          (house != null ? house.getNumberOfFloors() : 1L));
-
-      house = new House(houseName, year, floors);
-    }
-
-    Date creationDate = new Date();
-
-    Flat updatedFlat = new Flat(
-        idToUpdate,
-        name,
-        coordinates,
-        creationDate,
-        area,
-        rooms,
-        furnish,
-        view,
-        transport,
-        house);
-
-    collection.put(idToUpdate, updatedFlat);
-    return "Flat with ID " + idToUpdate + " was successfully updated.";
-  }
 }

app/src/main/java/itmo/lab5/cli/helpers/History.java

@@ -3,10 +3,20 @@ package itmo.lab5.cli.helpers;
 import java.util.ArrayDeque;
 import java.util.Deque;
 
+/**
+ * Manages the history of executed commands, maintaining a fixed size.
+ */
 public class History {
-  private static final int MAX_SIZE = 8;
-  private final Deque<String> history = new ArrayDeque<String>(MAX_SIZE);
   
+  private static final int MAX_SIZE = 8;
+  private final Deque<String> history = new ArrayDeque<>(MAX_SIZE);
+
+  /**
+   * Adds a command to the history. If the history exceeds the maximum
+   * size, the oldest command is removed.
+   *
+   * @param command the command to add to the history.
+   */
   public void add(String command) {
     if (history.size() >= MAX_SIZE)
       history.removeFirst();
@@ -14,17 +24,36 @@ public class History {
     history.add(command);
   }
 
+  /**
+   * Retrieves a command from the history by its index.
+   *
+   * @param x the index of the command to retrieve.
+   * @return the command at the specified index, or an empty string
+   *         if the index is out of bounds.
+   */
   public String get(int x) {
-    if (x >= MAX_SIZE)
+    if (x >= MAX_SIZE || x < 0)
       return "";
 
     return (String) history.toArray()[x];
   }
 
+  /**
+   * Returns a string representation of the entire command history.
+   *
+   * @return a string listing all commands in the history.
+   */
   public String get() {
     return history.toString();
   }
 
+  /**
+   * Returns a formatted string representation of the command history.
+   *
+   * @return a string that lists all commands in the history with
+   *         a prefix.
+   */
+  @Override
   public String toString() {
     var builder = new StringBuilder("History: \n");
     history.forEach(command -> builder.append(" - " + command + "\n"));

app/src/main/java/itmo/lab5/cli/helpers/ReaderUtil.java

@@ -3,13 +3,30 @@ package itmo.lab5.cli.helpers;
 import java.util.Arrays;
 import java.util.Scanner;
 
+/**
+ * Utility class for reading user input with various prompt methods.
+ */
 public class ReaderUtil {
+  
   private final Scanner scanner;
 
+  /**
+   * Constructs a ReaderUtil with the specified Scanner for input.
+   *
+   * @param scanner the Scanner to read user input.
+   */
   public ReaderUtil(Scanner scanner) {
     this.scanner = scanner;
   }
 
+  /**
+   * Prompts the user for a string input, allowing for an optional old value.
+   *
+   * @param message the message to display to the user.
+   * @param allowEmpty whether to allow empty input.
+   * @param oldValue the previous value to display as a hint.
+   * @return the user input or the old value if input is empty.
+   */
   public String promptString(String message, boolean allowEmpty, String oldValue) {
     while (true) {
       System.out.print(message);
@@ -27,6 +44,15 @@ public class ReaderUtil {
     }
   }
 
+  /**
+   * Prompts the user to select an enum value from the specified options.
+   *
+   * @param message the message to display to the user.
+   * @param enumClass the class of the enum type.
+   * @param oldValue the previous value to display as a hint.
+   * @param <T> the type of the enum.
+   * @return the selected enum value or the old value if input is empty.
+   */
   public <T extends Enum<T>> T promptEnum(String message, Class<T> enumClass, T oldValue) {
     while (true) {
       if (oldValue != null)
@@ -34,8 +60,8 @@ public class ReaderUtil {
 
       System.out.print(
           message + "(options: " +
-              String.join(", ", Arrays.stream(enumClass.getEnumConstants()).map(Enum::name).toList()) +
+              String.join(", ", Arrays.stream(enumClass.getEnumConstants())
-              "): ");
+              .map(Enum::name).toList()) + "): ");
 
       String input = scanner.nextLine().trim();
 
@@ -46,10 +72,18 @@ public class ReaderUtil {
       } catch (IllegalArgumentException e) {
         System.out.println("Invalid name; Please, try again: ");
       }
-
     }
   }
 
+  /**
+   * Prompts the user to select an enum value, allowing for a nullable option.
+   *
+   * @param message the message to display to the user.
+   * @param enumClass the class of the enum type.
+   * @param oldValue the previous value to display as a hint.
+   * @param <T> the type of the enum.
+   * @return the selected enum value or the old value if input is empty.
+   */
   public <T extends Enum<T>> T promptEnumNullable(String message, Class<T> enumClass, T oldValue) {
     while (true) {
       if (oldValue != null)
@@ -57,8 +91,8 @@ public class ReaderUtil {
 
       System.out.print(
           message + "(options: " +
-              String.join(", ", Arrays.stream(enumClass.getEnumConstants()).map(Enum::name).toList()) +
+              String.join(", ", Arrays.stream(enumClass.getEnumConstants())
-              "): ");
+              .map(Enum::name).toList()) + "): ");
 
       String input = scanner.nextLine().trim();
 
@@ -72,6 +106,17 @@ public class ReaderUtil {
     }
   }
 
+  /**
+   * Prompts the user for a number input within specified bounds.
+   *
+   * @param message the message to display to the user.
+   * @param min the minimum acceptable value.
+   * @param max the maximum acceptable value.
+   * @param parser the parser to convert input to the desired type.
+   * @param oldValue the previous value to display as a hint.
+   * @param <T> the type of the number, which must be comparable.
+   * @return the user input as a number or the old value if input is empty.
+   */
   public <T extends Comparable<T>> T promptNumber(String message, T min, T max, Parser<T> parser, T oldValue) {
     while (true) {
       System.out.print(message + " (" + oldValue + "): ");

app/src/main/java/itmo/lab5/interfaces/Command.java

@@ -2,6 +2,18 @@ package itmo.lab5.interfaces;
 
 import itmo.lab5.cli.CommandContext;
 
+/**
+ * Represents a command that can be executed with a set of arguments
+ * and a command context.
+ */
 public interface Command {
+  
+  /**
+   * Executes the command with the provided arguments and context.
+   *
+   * @param args an array of arguments to be used during execution.
+   * @param context the context in which the command is executed.
+   * @return a string representing the result of the command execution.
+   */
   String execute(String[] args, CommandContext context);
 }

app/src/main/java/itmo/lab5/models/Coordinates.java

@@ -1,5 +1,8 @@
 package itmo.lab5.models;
 
+/**
+ * Represents a point in the provided task.
+ */
 public class Coordinates {
   private int x;
   private Long y; // Поле не может быть null

app/src/main/java/itmo/lab5/models/Flat.java

@@ -5,6 +5,9 @@ import itmo.lab5.models.enums.*;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 
+/**
+ * Represents a flat, provided by se.ifmo.ru (no 462025)
+ */
 public class Flat {
   private int id; // Значение поля должно быть больше 0, Значение этого поля должно быть
                   // уникальным, Значение этого поля должно генерироваться автоматически
@@ -19,6 +22,20 @@ public class Flat {
   private Transport transport; // Поле не может быть null
   private House house; // Поле может быть null
 
+  /**
+   * Constructs a Flat object with the specified attributes.
+   *
+   * @param id the unique identifier of the flat (must be greater than 0).
+   * @param name the name of the flat (must not be null or empty).
+   * @param coordinates the coordinates of the flat (must not be null).
+   * @param creationDate the creation date of the flat (must not be null).
+   * @param area the area of the flat (must be greater than 0 and less than or equal to 626).
+   * @param numberOfRooms the number of rooms in the flat (must be greater than 0).
+   * @param furnish the furnish type of the flat (must not be null).
+   * @param view the view from the flat (can be null).
+   * @param transport the transport type associated with the flat (must not be null).
+   * @param house the house details associated with the flat (can be null).
+   */
   public Flat(int id, String name, Coordinates coordinates, Date creationDate, Double area,
       int numberOfRooms, Furnish furnish, View view, Transport transport, House house) {
     this.id = id;
@@ -33,90 +50,201 @@ public class Flat {
     this.house = house;
   }
   
+  /**
+   * Default constructor for creating an empty Flat object.
+   */
   public Flat() {
 
   }
 
+  /**
+   * Gets the unique identifier of the flat.
+   *
+   * @return the id of the flat.
+   */
   public int getId() {
     return id;
   }
 
+  /**
+   * Sets the unique identifier of the flat.
+   *
+   * @param id the new id of the flat (must be greater than 0).
+   */
   public void setId(int id) {
     this.id = id;
   }
   
+  /**
+   * Gets the name of the flat.
+   *
+   * @return the name of the flat.
+   */
   public String getName() {
     return name;
   }
 
+  /**
+   * Sets the name of the flat.
+   *
+   * @param name the new name of the flat (must not be null or empty).
+   */
   public void setName(String name) {
     this.name = name;
   }
 
+  /**
+   * Gets the coordinates of the flat.
+   *
+   * @return the coordinates of the flat (must not be null).
+   */
   public Coordinates getCoordinates() {
     return coordinates;
   }
 
+  /**
+   * Sets the coordinates of the flat.
+   *
+   * @param coordinates the new coordinates of the flat (must not be null).
+   */
   public void setCoordinates(Coordinates coordinates) {
     this.coordinates = coordinates;
   }
 
+  /**
+   * Gets the creation date of the flat.
+   *
+   * @return the creation date of the flat (must not be null).
+   */
   public Date getCreationDate() {
     return creationDate;
   }
 
+  /**
+   * Sets the creation date of the flat.
+   *
+   * @param creationDate the new creation date of the flat (must not be null).
+   */
   public void setCreationDate(Date creationDate) {
     this.creationDate = creationDate;
   }
   
+  /**
+   * Gets the area of the flat.
+   *
+   * @return the area of the flat (must be greater than 0 and less than or equal to 626).
+   */
   public Double getArea() {
     return area;
   }
 
+  /**
+   * Sets the area of the flat.
+   *
+   * @param area the new area of the flat (must be greater than 0 and less than or equal to 626).
+   */
   public void setArea(Double area) {
     this.area = area;
   }
   
+  /**
+   * Gets the number of rooms in the flat.
+   *
+   * @return the number of rooms in the flat (must be greater than 0).
+   */
   public int getNumberOfRooms() {
     return numberOfRooms;
   }
 
+  /**
+   * Sets the number of rooms in the flat.
+   *
+   * @param numberOfRooms the new number of rooms in the flat (must be greater than 0).
+   */
   public void setNumberOfRooms(int numberOfRooms) {
     this.numberOfRooms = numberOfRooms;
   }
 
+  /**
+   * Gets the furnish type of the flat.
+   *
+   * @return the furnish type of the flat (must not be null).
+   */
   public Furnish getFurnish() {
     return furnish;
   }
 
+  /**
+   * Sets the furnish type of the flat.
+   *
+   * @param furnish the new furnish type of the flat (must not be null).
+   */
   public void setFurnish(Furnish furnish) {
     this.furnish = furnish;
   }
 
+  /**
+   * Gets the view from the flat.
+   *
+   * @return the view from the flat (can be null).
+   */
   public View getView() {
     return view;
   }
 
+  /**
+   * Sets the view from the flat.
+   *
+   * @param view the new view from the flat (can be null).
+   */
   public void setView(View view) {
     this.view = view;
   }
 
+  /**
+   * Gets the transport type associated with the flat.
+   *
+   * @return the transport type associated with this class
+   */ 
   public Transport getTransport() {
     return transport;
   }
   
+  
+ /**
+  * Sets the transport associated with this flat.
+  *
+  * @param transport the transport to be set
+  */
   public void setTransport(Transport transport) {
     this.transport = transport;
   }
   
+ /**
+  * Returns the house associated with this flat.
+  *
+  * @return the house
+  */
   public House getHouse() {
     return house;
   }
 
+ /**
+  * Sets the house associated with this flat.
+  *
+  * @param house the house to be set
+  */
   public void setHouse(House house) {
     this.house = house;
   }
   
+ /**
+  * Returns a string representation of the flat, including its ID, name,
+  * coordinates, creation date, area, number of rooms, furnishing status,
+  * view, transport, and house.
+  *
+  * @return a string representation of the flat
+  */
   @Override
   public String toString() {
     var sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");

app/src/main/java/itmo/lab5/models/House.java

@@ -1,28 +1,64 @@
 package itmo.lab5.models;
 
+
+/**
+ * Represents a house with a name, year of construction, and number of floors.
+ * The name cannot be null, the year must be greater than 0 and less than or equal to 959,
+ * and the number of floors must be greater than 0 and less than or equal to 77.
+ */
 public class House {
   private String name; // Поле не может быть null
   private int year; // Максимальное значение поля: 959, Значение поля должно быть больше 0
   private long numberOfFloors; // Максимальное значение поля: 77, Значение поля должно быть больше 0
 
+ /**
+  * Constructs a House with the specified name, year, and number of floors.
+  *
+  * @param name the name of the house, must not be null
+  * @param year the year of construction, must be greater than 0 and less
+  * than or equal to 959
+  * @param numberOfFloors the number of floors, must be greater than 0 and
+  * less than or equal to 77
+  */
   public House(String name, int year, long numberOfFloors) {
     this.name = name;
     this.year = year;
     this.numberOfFloors = numberOfFloors;
   }
 
+ /**
+  * Returns the name of the house.
+  *
+  * @return the name of the house
+  */
   public String getName() {
     return this.name;
   }
 
+ /**
+  * Returns the year of construction of the house.
+  *
+  * @return the year of construction
+  */
   public int getYear() {
     return this.year;
   }
 
+ /**
+  * Returns the number of floors in the house.
+  *
+  * @return the number of floors
+  */
   public long getNumberOfFloors() {
     return this.numberOfFloors;
   }
 
+ /**
+  * Returns a string representation of the house, including its name, year of construction,
+  * and number of floors.
+  *
+  * @return a string representation of the house
+  */
   public String toString() {
     return "House(" +
         "name = '" + name +

app/src/main/java/itmo/lab5/models/enums/Furnish.java

@@ -1,5 +1,8 @@
 package itmo.lab5.models.enums;
 
+/**
+ * Represents the different types of furnishing available for a flat.
+ */
 public enum Furnish {
   DESIGNER,
   FINE,

app/src/main/java/itmo/lab5/models/enums/Transport.java

@@ -1,5 +1,8 @@
 package itmo.lab5.models.enums;
 
+/**
+ * Represents the different *strange* levels of transport
+ */
 public enum Transport {
   FEW,
   NONE,

app/src/main/java/itmo/lab5/models/enums/View.java

@@ -1,5 +1,8 @@
 package itmo.lab5.models.enums;
 
+/**
+ * Represents the different types of views available from a flat.
+ */
 public enum View {
   STREET,
   PARK,

app/src/main/java/itmo/lab5/parser/Writer.java

@@ -0,0 +1,50 @@
+package itmo.lab5.parser;
+
+import java.io.*;
+import java.text.SimpleDateFormat;
+import java.util.HashMap;
+
+import itmo.lab5.models.Flat;
+
+public class Writer {
+  static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
+
+  public String writeCollection(String filename, HashMap<Integer, Flat> flats) {
+    try (FileOutputStream fos = new FileOutputStream(filename);
+        OutputStreamWriter osw = new OutputStreamWriter(fos);
+        BufferedWriter writer = new BufferedWriter(osw)) {
+
+      for (Flat flat : flats.values()) {
+        String date = "";
+
+        try {
+          date = dateFormat.format(flat.getCreationDate()).toString();
+        } catch (Exception e) {
+          System.out.println(e.getMessage());
+        }
+
+        String line = String.format("%d,%s,%d,%d,%s,%.2f,%d,%s,%s,%s,%s,%d,%d\n",
+            flat.getId(),
+            flat.getName(),
+            flat.getCoordinates().getX(),
+            flat.getCoordinates().getY(),
+            date,
+            flat.getArea(),
+            flat.getNumberOfRooms(),
+            flat.getFurnish(),
+            flat.getView() != null ? flat.getView() : "",
+            flat.getTransport(),
+            flat.getHouse() != null ? flat.getHouse().getName() : "",
+            flat.getHouse() != null ? flat.getHouse().getYear() : 0,
+            flat.getHouse() != null ? flat.getHouse().getNumberOfFloors() : 0);
+
+        writer.write(line);
+      }
+
+      return "Collection has been saved to the file successfully.";
+    } catch (IOException e) {
+      e.printStackTrace();
+      return "An error occurred while saving the collection to file.";
+    }
+  }
+}