Code in Java pls

UndoRedoPainter.java, filling in the undo$()$ method as follows:

Your code should get the history stack from the superclass, pop off the top Circle object, and then call repaint$().($Don$$t call paintComponent$()$ directly $...$ the reason is too complicated to explain here.$)$

To test, run UndoRedoPainter.java as an app. Add a red circle, then a green circle, then a blue circle.

If you click the Undo button, what should happen? Now click the Undo button. Is this the result you expect? If not, make sure to go back and debug your code. Using the debugger, will allow you to examine the contents of the history and undoHistory stacks.

Here is the code so far:

package stacklab;

import java.util.$*$;

public class UndoRedoPainter extends Painter $\{$

public UndoRedoPainter$()\{$

setUndoButtonEnabled$($false$)$;

setRedoButtonEnabled$($false$)$;

$\}$

$//$ Called when the user pushes the Undo button.

void undo$()\{$

$\}$

$//$ Called when the user pushes the Redo button.

@Override

void redo$()\{$

$\}$

public static void main$($String$[]$ args$)$

$\{$

new UndoRedoPainter$().$setVisible$($true$)$;

$\}$

$\}$

package stacklab;

import java.awt.$*$;

import java.awt.event.$*$;

import java.util.$*$;

import javax.swing.$*$;

import javax.swing.event.$*$;

public class Painter extends JFrame implements ActionListener $\{$

private Painter outerThis;

private JButton undoBtn;

private JButton redoBtn;

private JButton quitBtn;

private ColorChooser colorChooser;

private Canvas canvas;

private Stack history;

private Stack undoHistory;

private class ColorChooser extends JPanel $\{$

JSlider$[]$ sliders;

SamplerPanel sampler;

ColorChooser$()\{$

setLayout$($new BorderLayout$())$;

sampler $=$ new SamplerPanel$()$;

JPanel west $=$ new JPanel$($new GridLayout$(3,1))$;

sliders $=$ new JSlider$[3]$;

for $($int i$=0$; i$<3$; i$++)\{$

JPanel p $=$ new JPanel$()$;

p$.$add$($new JLabel$(""+"$RGB$".$charAt$($i$)))$;

sliders$[$i$]=$ new JSlider$(0,255,($i$==0)?255$ : $0)$;

sliders$[$i$].$addChangeListener$($sampler$)$;

p$.$add$($sliders$[$i$])$;

west.add$($p$)$;

$\}$

add$($west$,$ BorderLayout.WEST$)$;

add$($sampler$,$ BorderLayout.CENTER$)$;

$\}$

Color getColor$()\{$

int r $=$ sliders$[0].$getValue$()$;

int g $=$ sliders$[1].$getValue$()$;

int b $=$ sliders$[2].$getValue$()$;

return new Color$($r$,$ g$,$ b$)$;

$\}$

private class SamplerPanel extends JPanel implements ChangeListener $\{$

public Dimension getPreferredSize$()$

$\{$

return new Dimension$(50,50)$;

$\}$

public void stateChanged$($ChangeEvent e$)$

$\{$

repaint$()$;

$\}$

public void paintComponent$($Graphics g$)$

$\{$

g$.$setColor$($getColor$())$;

g$.$fillRect$(0,0,$ getWidth$(),$ getHeight$())$;

$\}$

$\}$

$\}$

private class Canvas extends JPanel implements MouseListener $\{$

Canvas$()\{$

addMouseListener$($this$)$;

$\}$

public Dimension getPreferredSize$()\{$

return new Dimension$(500,500)$;

$\}$

public void mouseClicked$($MouseEvent e$)\{$

Circle circle $=$ new Circle$($e$.$getPoint$(),50,$ colorChooser.getColor$())$;

history.push$($circle$)$;

repaint$()$;

undoBtn.setEnabled$($true$)$;

$\}$

public void mousePressed$($MouseEvent e$)\{\}$

public void mouseReleased$($MouseEvent e$)\{\}$

public void mouseEntered$($MouseEvent e$)\{\}$

public void mouseExited$($MouseEvent e$)\{\}$

public void paintComponent$($Graphics g$)\{$

g$.$setColor$($Color$.$WHITE$)$;

g$.$fillRect$(0,0,$ getWidth$(),$ getHeight$())$;

for $($Circle circle: history$)$

circle.paint$($g$)$;

$\}$

$\}//$ End of inner class Canvas

Painter$()\{$

outerThis $=$ this;

setResizable$($false$)$;

setDefaultCloseOperation$($JFrame$.$EXIT$\_$ON$\_$CLOSE$)$;

history $=$ new Stack$<>()$;

undoHistory $=$ new Stack$<>()$;

JPanel pan $=$ new JPanel$()$;

colorChooser $=$ new ColorChooser$()$;

pan.add$($colorChooser$)$;

undoBtn $=$ new JButton$("$Undo$")$;

undoBtn.addActionListener$($this$)$;

pan.add$($undoBtn$)$;

redoBtn $=$ new JButton$("$Redo$")$;

redoBtn.addActionListener$($this$)$;

pan.add$($redoBtn$)$;

quitBtn $=$ new JButton$("$Quit$")$;

quitBtn.addActionListener$($this$)$;

pan.add$($quitBtn$)$;

add$($pan$,$ BorderLayout.NORTH$)$;

setCanvas$($new Canvas$())$;

add$($getCanvas$(),$ BorderLayout.CENTER$)$;

pack$()$;

$\}$

public void actionPerformed$($ActionEvent e$)\{$

if $($e$.$getSource$()==$ quitBtn$)$

System.exit$(0)$;

else if $($e$.$getSource$()==$ undoBtn$)$

undo$()$;

else if $($e$.$getSource$()==$ redoBtn$)$

redo$()$;

$\}$

void undo$()\{$

System.out.println$("$Undo not implemented"$)$;

$\}$

void redo$()\{$

System.out.println$("$Redo not implemented"$)$;

$\}$

Stack getHistory$()\{$

return history;

$\}$

Stack getUndoHistory$()\{$

return undoHistory;

$\}$

void setUndoButtonEnabled$($boolean b$)\{$

undoBtn.setEnabled$($b$)$;

$\}$

void setRedoButtonEnabled$($boolean b$)\{$

redoBtn.setEnabled$($b$)$;

$\}$

public static void main$($String$[]$ args$)\{$

new Painter$().$setVisible$($true$)$;

$\}$

public Canvas getCanvas$()\{$

return canvas;

$\}$

public void setCanvas$($Canvas canvas$)\{$

this.canvas $=$ canvas;

$\}$

$\}$