1． Calculator类
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.*;
import java.applet.Applet;
import javax.swing.*;
import javax.swing.border.*;
public class Calculator extends JApplet implements ActionListener
{
private final String[] KEYS={"7","8","9","/","sqrt",
"4","5","6","*","%",
"1","2","3","-","1/x",
"0","+/-",".","+","="
};
private final String[] COMMAND={"Backspace","CE","C"};
private final String[] M={" ","MC","MR","MS","M+"};
private JButton keys[]=new JButton[KEYS.length];
private JButton commands[]=new JButton[COMMAND.length];
private JButton m[]=new JButton[M.length];
private JTextField display =new JTextField("0");
// public JTextField setHorizontalAlignment(int alignment);
// private JTextField
display.setHorizontalAlignment(JTextField.RIGHT)=new JTextField("0");
private void setup()
{
display.setHorizontalAlignment(JTextField. RIGHT);
JPanel calckeys=new JPanel();
JPanel command=new JPanel();
JPanel calms=new JPanel();
calckeys.setLayout(new GridLayout(4,5,3,3));
command.setLayout(new GridLayout(1,3,3,3));
calms.setLayout(new GridLayout(5,1,3,3));
for(int i=0;i<KEYS.length;i++)
{
keys[i]=new JButton(KEYS[i]);
calckeys.add(keys[i]);
keys[i].setForeground(Color. blue);
}
keys[3].setForeground(Color. red);
keys[4].setForeground(Color. red);
keys[8].setForeground(Color. red);
keys[9].setForeground(Color. red);
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