Color Change

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

class colorchange extends JPanel implements ActionListener{

static JFrame frame1;

JButton b1;

JButton b2;

JButton b3;

public colorchange(){

b1=new JButton("Red");

b2=new JButton("Green");

b3=new JButton("Blue");

b1.setMnemonic('R');

b2.setMnemonic('G');

b3.setMnemonic('B');

b1.setToolTipText("Red");

b1.addActionListener(this);

b2.addActionListener(this);

b3.addActionListener(this);

add(b1);

add(b2);

add(b3);

b1.requestFocus();

}

public void actionPerformed(ActionEvent evt){

Object source=evt.getSource();

if(source==b1)

setBackground(Color.red);

else if(source==b2)

setBackground(Color.green);

else if(source==b3)

setBackground(Color.blue);

}

public static void main(String[] a){

frame1=new JFrame("Color Change");

colorchange c1=new colorchange();

frame1.getContentPane().add("Center",c1);

frame1.setSize(200,150);

frame1.addWindowListener(new WindowAdapter(){

public void WindoClosing(WindowEvent e){

System.exit(0);

}

});

frame1.setVisible(true);

}

}

Find prime number

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

class Findprimes extends JFrame implements Runnable, ActionListener{
Thread go;
JLabel howmanylabel=new JLabel("Quantity: ");
JTextField howmany=new JTextField("400",10);
JButton display=new JButton("Display primes");
JTextArea primes=new JTextArea(8,40);

Findprimes(){
super("Find prime Numbers");
setSize(400,300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container content=getContentPane();
BorderLayout bord=new BorderLayout();
content.setLayout(bord);
display.addActionListener(this);

JPanel topPanel=new JPanel();
topPanel.add(howmanylabel);
topPanel.add(howmany);
topPanel.add(display);

content.add(topPanel,BorderLayout.NORTH);
primes.setLineWrap(true);
JScrollPane textPane=new JScrollPane(primes);
content.add(textPane,BorderLayout.CENTER);
setVisible(true);
}
public void actionPerformed(ActionEvent evt){
display.setEnabled(true);
if(go==null){
go=new Thread(this);
go.start();
}

}
public void run(){
int quantity=Integer.parseInt(howmany.getText());
int numprimes=0;
int candidate=2;
primes.append("First "+quantity+" primes;");
while(numprimes<quantity){
if(isPrime(candidate)){
primes.append(candidate+" ");
numprimes++;
}
candidate++;
}
}
public static boolean isPrime(int checkNumber){
double root=Math.sqrt(checkNumber);
for(int i=2;i<root;i++){
if(checkNumber%i==0)
return false;
}
return true;
}
public static void main(String[] a){
Findprimes fp=new Findprimes();

}
}