[PHP知识库]java——图形输入输出

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

public class AppGraphIO {
    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("用于显示结果的标签");

    public AppFrame(){
        //设置流式布局，加进来的东西一个个接着放，到下一排
        setLayout( new FlowLayout() );
        getContentPane().add( in );
        getContentPane().add( btn );
        getContentPane().add( out );
        //设置点击事件监听
        btn.addActionListener( new BtnActionAdpter() );
        setSize(400,100);
        //设置关闭键
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        setVisible(true);
    }

    class BtnActionAdpter implements ActionListener{
        public void actionPerformed(ActionEvent e){
            //抓取，解析，处理，显示
            String s = in.getText();
            double d = Double.parseDouble(s);
            double sq = d * d;
            out.setText(d + "的平方：" + sq);
        }
    }
}

结果显示：

java8的改进：lambda表达式

        btn.addActionListener( e->{
            //抓取，解析，处理，显示
            String s = in.getText();
            double d = Double.parseDouble(s);
            double sq = d * d;
            out.setText(d + "的平方：" + sq);
        } );