java 抛空指针异常

来源：百度知道 编辑：UC知道 时间：2024/06/15 04:36:16
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class TextFieldTest
{ public static void main(String arg[])
{
TextFieldFrame tff = new TextFieldFrame();
tff.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
tff.show();
}
}

class TextFieldFrame extends JFrame
{
public TextFieldFrame()
{
setTitle("练习");
setSize(WIDTH,HEIGHT);

Container contentpane = getContentPane();

//新建文档监听器
DocumentListener resultListener = new ResultListener();

//建立容纳文本域的面板
JPanel TextPanel = new JPanel();
JTextField Text1 = new JTextField("",20);
//为第一个文本域安装监听器

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

public class TextFieldTest
{ public static void main(String arg[])
{
TextFieldFrame tff = new TextFieldFrame();
tff.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
tff.setVisible(true);
}
}

class TextFieldFrame extends JFrame
{
JTextField Text1 ;
JTextField Text2 ;
JTextField Text3 ;
public TextFieldFrame()
{
setTitle("练习");
setSize(WIDTH,HEIGHT);

Container contentpane = getContentPane();

//新建文档监听器
DocumentListener resultListener = new ResultListener();

//建立容纳文本域的面板
JPanel TextPanel = new JPanel();
Text1 = new JTextField("",20);
//为第一个文本域安装监听器
Text1.getDocument().addDocumentListener(resultListener);

Text2 = new JTextField("",20);
Text2.getDocument().add