5.29合計ウィンドウのJava

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

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class GridLayoutPosition extends JFrame{
    JLabel jl1;
    JLabel jl2;
    JButton jb1;
    JButton jb2;
    JTextField jt1;
    JTextField jt2;
    JTextField jt3;
    public GridLayoutPosition(){
        jl1 = new JLabel("加数1");
        jl2 = new JLabel("加数2");
        jb1 =new JButton("求和");
        jb2 =new JButton("清除");
        jt1 = new JTextField();
        jt2 = new JTextField();
        jt3 = new JTextField();
        Container c = getContentPane();
        setLayout(new GridLayout(3,3,2,2));
        c.add(jl1);
        c.add(jt1);
        c.add(new JLabel());
        c.add(jl2);
        c.add(jt2);
        c.add(new JLabel());
        c.add(jb1);
        jb1.addActionListener(new jbListener());
        c.add(jt3);
        c.add(jb2);
        jb2.addActionListener(new jbListener());    
        setSize(300,150);
        setTitle("求和计算");
        setVisible(true);
        setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    }
    class jbListener implements ActionListener{
        public void actionPerformed(ActionEvent e) {
            JButton jbInput= (JButton)e.getSource();
            if(jbInput.equals(jb1)) {
                String a1=jt1.getText();
                int i = Integer.parseInt(a1);
                String a2=jt2.getText();
                int j = Integer.parseInt(a2);
                jt3.setText(""+(i+j));
            }else if(jbInput.equals(jb2)){
                jt1.setText("");
                jt2.setText("");
                jt3.setText("");
            }
            
        }
    }
    public static void main(String[] args) {
        new GridLayoutPosition();
    }

}