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Question about the task

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11.1. Add an UndoManager undoManager field to the view. Figure out what this class is used for. Initialize the field with a new object.
11.2. In the listeners package, add an UndoListener class that implements the UndoableEditListener interface. This class will listen for edits that can undone or redone.
11.3. Add the following to the UndoListener class:
11.3.1. An UndoManager undoManager field.
11.3.2. A constructor that takes an UndoManager and initializes the corresponding field.
11.3.3. An undoableEditHappened(undoableEditEvent e) method. It should get the edit from the passed event and add it to undoManager.
11.4. Add an UndoListener undoListener field to the view, and initialize it using undoManager.
11.5. Add the following methods to the view:
11.5.1. void undo() - This method undoes the last action. Implement it using undoManager.
The method must not throw exceptions. It should only log them.
11.5.2. void redo() - This method returns the previously undone action. Implement it by analogy with the previous step.
11.5.3. Implement boolean canUndo() and boolean canRedo() methods using undoManager.
11.5.4. Implement a getter for undoListener.
11.5.5. Add and implement a void resetUndo() method that clears all edits in undoManager.

Requirements:

The View class must have a private UndoManager undoManager field, which must be immediately initialized.
The View class must have a private UndoListener undoListener field, which must be immediately initialized using the undoManager field.
The View class must have a getter for the UndoListener undoListener field.
The View class must have a public void undo() method.
The View class must have a public void redo() method.
The implementation of the View class's canUndo() method should use undoManager.
The implementation of the View class's canRedo() method should use undoManager.
The View class should have a public void resetUndo() method, which should clear all edits in undoManager.
The UndoListener class must be in a separate file.
The UndoListener class must have a private UndoManager undoManager field.
The UndoListener(UndoManager undoManager) must correctly initialize the undoManager field.
The undoableEditHappened(UndoableEditEvent e) method in the UndoListener class should get the edit from the passed event and add it to undoManager.

package com.codegym.task.task32.task3209; import javax.swing.text.html.HTMLDocument; import java.io.File; public class Controller { private View view; private HTMLDocument document; private File currentFile; public Controller(View view) { this.view = view; } public void init() {} public void exit() { System.exit(0); } public static void main(String[] args) { View view = new View(); Controller controller = new Controller(view); view.setController(controller); view.init(); controller.init(); } public static class ExceptionHandler { public static void log(Exception e) { } } }