4.17今日总结

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;/**包含JFrame*/
public class AppGraphInOut {
public static void main(String args[]){
new AppFrame();
}
}

class AppFrame extends JFrame
{
JTextField in=new JTextField(10);
JButton btn=new JButton("求平方");
JLabel out=new JLabel("用于显示平方结果的标签");
public AppFrame()
{
setLayout(new FlowLayout());
getContentPane().add(in);
getContentPane().add(btn);
getContentPane().add(out);
btn.addActionListener(new BtnActionAdapter());
setSize(400,100);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setVisible(true);
}

class BtnActionAdapter implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String s=in.getText();
double d=Double.parseDouble(s);
double sq=d*d;
out.setText(d+"的平方是："+sq);
}
}

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原文链接：https://blog.csdn.net/salmonwilliam/article/details/81952387