java GUI计算器

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class jisuanqi extends JFrame implements ActionListener{
private JTextField jtf1;
private JButton btn[];
private String s1="";
private int n=0;
private int[] fh=new int[10];String[] sr;double sum;
JPanel p1=new JPanel(),
p2=new JPanel();
public jisuanqi(){
String str[]={"7","8","9","/","4","5","6","*","1","2","3","-","0",".","=","+"};
btn=new JButton[str.length];     //创建按钮数组
for(int i=0;i<str.length;i++){
btn[i]=new JButton(str[i]);
p2.add(btn[i]);
btn[i].addActionListener(this);
}
setTitle("计算器");
JLabel a=new JLabel();
JLabel b=new JLabel();
JLabel c=new JLabel();
JLabel d=new JLabel();
p1.setLayout(new BorderLayout(15,15));
p1.add(jtf1=new JTextField("0",20),BorderLayout.CENTER);
jtf1.setHorizontalAlignment(JTextField.RIGHT);      //右对齐
p1.add(a,BorderLayout.PAGE_START);
p1.add(b,BorderLayout.LINE_START);
p1.add(c,BorderLayout.LINE_END);
p1.add(d,BorderLayout.PAGE_END);
jtf1.setEditable(false);                   //文本框不可编辑
p2.setLayout(new GridLayout(4,4,2,2));
setLayout(new BorderLayout(2,2));
add(p1,BorderLayout.NORTH);
add(p2,BorderLayout.CENTER);
pack();
setVisible(true);
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed(ActionEvent e){
String cmd=e.getActionCommand();
if(cmd.equals("1")){
s1+='1';jtf1.setText(s1);
}
else if(cmd.equals("2")){
s1+='2';jtf1.setText(s1);
}
else if(cmd.equals("3")){
s1+='3';jtf1.setText(s1);
}
else if(cmd.equals("4")){
s1+='4';jtf1.setText(s1);
}
else if(cmd.equals("5")){
s1+='5';jtf1.setText(s1);
}
else if(cmd.equals("6")){
s1+='6';jtf1.setText(s1);
}
else if(cmd.equals("7")){
s1+='7';jtf1.setText(s1);
}
else if(cmd.equals("8")){
s1+='8';jtf1.setText(s1);
}
else if(cmd.equals("9")){
s1+='9';jtf1.setText(s1);
}
else if(cmd.equals("0")){
s1+='0';jtf1.setText(s1);
}
else if(cmd.equals(".")){       //防止误输入
if(s1==""){s1="0.";jtf1.setText(s1);}
else{s1+='.';jtf1.setText(s1);}
}
else if(cmd.equals("+")){
s1+='+';jtf1.setText(s1);
fh[n++]=1;
}
else if(cmd.equals("-")){
s1+='-';jtf1.setText(s1);
fh[n++]=2;
}
else if(cmd.equals("*")){
s1+='*';jtf1.setText(s1);
fh[n++]=3;
}
else if(cmd.equals("/")){
s1+='/';jtf1.setText(s1);
fh[n++]=4;
}
else if(cmd.equals("=")){
sr=s1.split("\\+|\\*|\\-|\\/");
//sr=s1.split("[*/+-]");//注意-在[]中代表范围，应放在两端，避免把小数点也隔离
sum=Double.parseDouble(sr[0]);
for(int i=1;i<sr.length;i++){
if(fh[i-1]==1)
sum+=Double.parseDouble(sr[i]);
else if(fh[i-1]==2)
sum-=Double.parseDouble(sr[i]);
else if(fh[i-1]==3)
sum*=Double.parseDouble(sr[i]);
else if(fh[i-1]==4){
if(sr[i].equals("0")){jtf1.setText("除数不能为0");n=0;s1="";return;} //
sum/=Double.parseDouble(sr[i]);
}
}
jtf1.setText(Double.toString(sum));
n=0;
s1="";
}
}
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new jisuanqi();
}
});
}
}