java 图形显示

import javax.swing.*;
import java.awt.*;
import java.awt.Event.*;
//从文本框中输入一个值。按回车键弹出对话框显示该输入值。
public class TestTextField extends JFrame

{
private TextField t1;
private Label l1;
public void TestTextField()
{
Container container=getContentPane();
container.setLayout(new BorderLayout());
JPanel j1=new JPanel();
JPanel j2=new JPanel();
l1=new Label("学生学号：");
t1=new TextField(5);
JButton jb1=new JButton("显示文本框内容");
j2.setLayout(new FlowLayout());
j2.add(l1);
j2.add(t1);
j1.add(jb1);
container.add(j1,BorderLayout.SOUTH);
container.add(j2,BorderLayout.NORTH);

}
public static void main(String args[])
{
TestTextField tt=new TestTextField();
tt.setSize(400,300);
tt.setTitle("Test TextFiled!");
tt.setVisible(true);
tt.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);