ButtonClear.java

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
import java.awt.FontMetrics;
class ButtonClear extends JButton
implements Command {
Mediator mediator;
ButtonClear(ActionListener al, Mediator med)
{
super(“Clear”);
addActionListener(al);
mediator = med;
mediator.registerClear(this);
}
public void execute() {
mediator.clear();
}
}

ButtonPrevious.java

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
import java.awt.FontMetrics;
class ButtonPrevious extends JButton
implements Command {
Mediator mediator;
ButtonPrevious(ActionListener al, Mediator
med) {
super(“Previous”);
addActionListener(al);
mediator = med;
mediator.registerPrevious(this);
}
public void execute() {
mediator.previous();
}
}

Display.java

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
import java.awt.FontMetrics;
class Display extends JLabel{
Mediator mediator;
Display (Mediator med) {
super(“0”,JLabel.CENTER);
mediator = med;
mediator.registerDisplay(this);
setBackground(Color.white);
setBorder(new EtchedBorder(Color.blue,
Color.green));
Font font = new Font(“Arial”,Font.BOLD,40);
setFont(font);
}
}

Mediator.java

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
import java.awt.FontMetrics;
class Mediator {
ButtonDice btnDc;
ButtonPrevious btnPrvs;
ButtonClear btnClr;
Display display;
java.util.List list, undo;
boolean restart = true;
int counter = 0, ct = 0;
//....
Mediator() {
list = new ArrayList();
undo = new ArrayList();
}
void registerDice(ButtonDice bd) {
btnDc = bd;
}
void registerClear(ButtonClear bc) {
btnClr = bc;
}
void registerPrevious(ButtonPrevious bp) {
btnPrvs = bp;