add Command pattern v4 implementation

Author: BuntyRaghani

command-pattern/src/main/java/com/example/command/v4/Application.java

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+package com.example.command.v4;
+
+public class Application {
+
+    public static void main(String[] args) {
+
+        var videoEditor = new VideoEditor();
+        var history = new History();
+
+        System.out.println("Initial State: " + videoEditor);
+
+        var setTextConcreteCommand = new SetTextConcreteCommand("Video Title", videoEditor, history);
+        setTextConcreteCommand.execute();
+        System.out.println("TEXT: " + videoEditor);
+
+        var setContrast = new SetContrastConcreteCommand(1, videoEditor, history);
+        setContrast.execute();
+        System.out.println("CONTRAST: " + videoEditor);
+
+        var undoConcreteCommand = new UndoConcreteCommand(history);
+        undoConcreteCommand.execute();
+        System.out.println("UNDO: " + videoEditor);
+
+        undoConcreteCommand.execute();
+        System.out.println("UNDO: " + videoEditor);
+    }
+}

command-pattern/src/main/java/com/example/command/v4/Command.java

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+package com.example.command.v4;
+
+public interface Command {
+
+    void execute();
+}

command-pattern/src/main/java/com/example/command/v4/History.java

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+package com.example.command.v4;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+public class History {
+    private Deque<UndoableCommand> undoableCommandDeque = new ArrayDeque<>();
+
+    public void push(UndoableCommand undoableCommand) {
+        undoableCommandDeque.push(undoableCommand);
+    }
+
+    public UndoableCommand pop() {
+        return undoableCommandDeque.pop();
+    }
+
+    public int size() {
+        return undoableCommandDeque.size();
+    }
+}

command-pattern/src/main/java/com/example/command/v4/SetContrastConcreteCommand.java

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+package com.example.command.v4;
+
+public class SetContrastConcreteCommand implements UndoableCommand {
+
+    private float contrast;
+    private float previousContrast;
+    private VideoEditor videoEditor;
+    private History history;
+
+    public SetContrastConcreteCommand(float contrast, VideoEditor videoEditor, History history) {
+        this.contrast = contrast;
+        this.videoEditor = videoEditor;
+        this.history = history;
+    }
+
+    @Override
+    public void execute() {
+        previousContrast = videoEditor.getContrast();
+        videoEditor.setContrast(contrast);
+        history.push(this);
+    }
+
+    @Override
+    public void unexecute() {
+        videoEditor.setContrast(previousContrast);
+    }
+}

command-pattern/src/main/java/com/example/command/v4/SetTextConcreteCommand.java

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+package com.example.command.v4;
+
+public class SetTextConcreteCommand implements UndoableCommand {
+
+    private String text;
+    private String previousText;
+    private VideoEditor videoEditor;
+    private History history;
+
+    public SetTextConcreteCommand(String text, VideoEditor videoEditor, History history) {
+        this.text = text;
+        this.videoEditor = videoEditor;
+        this.history = history;
+    }
+
+    @Override
+    public void execute() {
+        previousText = videoEditor.getText();
+        videoEditor.setText(text);
+        history.push(this);
+    }
+
+    @Override
+    public void unexecute() {
+        videoEditor.setText(previousText);
+    }
+}

command-pattern/src/main/java/com/example/command/v4/UndoConcreteCommand.java

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+package com.example.command.v4;
+
+public class UndoConcreteCommand implements Command {
+
+    private History history;
+
+    public UndoConcreteCommand(History history) {
+        this.history = history;
+    }
+
+    @Override
+    public void execute() {
+        if (history.size() > 0) {
+            history.pop().unexecute();
+        }
+    }
+}

command-pattern/src/main/java/com/example/command/v4/UndoableCommand.java

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+package com.example.command.v4;
+
+public interface UndoableCommand extends Command {
+
+    void unexecute();
+}

command-pattern/src/main/java/com/example/command/v4/VideoEditor.java

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+package com.example.command.v4;
+
+public class VideoEditor {
+
+    private float contrast;
+    private String text;
+
+    public float getContrast() {
+        return contrast;
+    }
+
+    public void setContrast(float contrast) {
+        this.contrast = contrast;
+    }
+
+    public String getText() {
+        return text;
+    }
+
+    public void setText(String text) {
+        this.text = text;
+    }
+
+    @Override
+    public String toString() {
+        return "VideoEditor{" +
+                "contrast=" + contrast +
+                ", text='" + text + '\'' +
+                '}';
+    }
+}