import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Gui{
JCheckBox right1=new JCheckBox("1");
JCheckBox right2=new JCheckBox("2");
JCheckBox right4=new JCheckBox("4");
JCheckBox right8=new JCheckBox("8");
StringBuffer choices;
JFrame frame=new JFrame("CheckBoxDemo");
JLabel displayLabel;
Gui()
{
right1.setMnemonic(KeyEvent.VK_4);
right1.setSelected(true);
right2.setMnemonic(KeyEvent.VK_3);
right2.setSelected(true);
right4.setMnemonic(KeyEvent.VK_2);
right4.setSelected(true);
right8.setMnemonic(KeyEvent.VK_1);
right8.setSelected(true);
CheckBoxListener myListener=new CheckBoxListener();
right1.addItemListener(myListener);
right2.addItemListener(myListener);
right4.addItemListener(myListener);
right8.addItemListener(myListener);
choices=new StringBuffer("0000");
displayLabel=new JLabel(choices.toString());
JPanel checkPanel=new JPanel();
checkPanel.setLayout(new GridLayout(0,1));
checkPanel.add(right1);
checkPanel.add(right2);
checkPanel.add(right4);
checkPanel.add(right8);
frame.getContentPane().setLayout(new BorderLayout());
frame.getContentPane().add(checkPanel,BorderLayout.WEST);
frame.getContentPane().add(displayLabel,BorderLayout.CENTER);
frame.setSize(500,500);
frame.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e)
{ System.exit(0);
}
});
// frame.pack(); 此处不用使用这个方法
frame.setVisible(true);
}
class CheckBoxListener implements ItemListener
{ public void itemStateChanged(ItemEvent e)
{ int index=0;
char c='-';
Object source =e.getItemSelectable();
if(source==right8)
{ index=0;
c='8';
}else if (source==right4)
{ index=1;
c='4';
}
else if (source==right2)
{ index=2;
c='2';
}
else if (source==right1)
{ index=3;
c='1';
}
if(e.getStateChange()==ItemEvent.DESELECTED)
c='-';
choices.setCharAt(index,c);
displayLabel.setText(choices.toString());
}
}
public static void main(String s[])
{ new Gui();
}
}