关于Exception in thread "main" java问题.lang.NullPointerException

Question

编译吧不报错   但执行 就会 出现 以下  内容
--------------------Configuration: <Default>--------------------
Exception in thread "main" java.lang.NullPointerException
    at java.util.Hashtable.put(Hashtable.java:399)
    at java.awt.GridBagLayout.setConstraints(GridBagLayout.java:482)
    at customerInfor.<init>(customerInfor.java:60)
    at customerInfor.main(customerInfor.java:172)Process completed.
源代码 是
//  客户信息 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class customerInfor extends JFrame
{
JButton SaveGroupInformationButton,DeleteInfoButton;
JLabel customerIDJlabel,customerNameJlabel,customerPhoneJlabel,
           contactMobilePhoneJlabel,contactNameJlabel,contactEmailJlabel,contactFaxJlable,
           contactAdressJlabel,custactpostcodeJlabel;
    JTextField customerIdField,customerNameField,customerPhomefield,customerMobiPhonefield,
               costactNameField,costactEmailField,contactFaxfield,contactAdressField,cunstactPosstcodeField; GridBagLayout g1;
GridBagConstraints  gbc;
public customerInfor(){
super("客户信息");
Container c=this.getContentPane();
customerIDJlabel=new JLabel("客户 ID");
customerIdField=new JTextField(20);
contactNameJlabel=new JLabel("客户姓名");
customerNameField=new JTextField(20);
        contactMobilePhoneJlabel=new JLabel("手机");
        customerMobiPhonefield=new JTextField(20);
        contactNameJlabel=new JLabel("联系人姓名");
        costactNameField=new JTextField(20);
        contactEmailJlabel=new JLabel("E-mail");
        costactEmailField=new JTextField(20);
        contactFaxJlable=new JLabel("传真");
        contactFaxfield=new JTextField(20);
        contactAdressJlabel=new JLabel("联系地址");
        contactAdressField=new JTextField(20);
        custactpostcodeJlabel=new JLabel("邮编");
        cunstactPosstcodeField=new JTextField(20);

g1=new GridBagLayout();
gbc=new GridBagConstraints();
c.setLayout(g1);

//给限定对象gbc的参数赋值

        
       // gbc.fill=GridBagConstraints.BOTH;
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=0;
        g1.setConstraints(customerIDJlabel,gbc);
        c.add(customerIDJlabel);
        
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=1;
        g1.setConstraints(customerIdField,gbc);
        c.add(customerIdField);
        
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=3;
        g1.setConstraints(customerNameJlabel,gbc);
        c.add(customerNameJlabel);
        
        
          
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=4;
        g1.setConstraints(customerNameField,gbc);
        c.add(customerNameField);
        
        gbc.weightx=1.0;
        gbc.gridx=1;
        gbc.gridy=0;
        g1.setConstraints(contactNameJlabel,gbc);
        c.add(contactNameJlabel);
        
        gbc.weightx=1.0;
        gbc.gridx=1;
        gbc.gridy=1;
        g1.setConstraints(costactNameField,gbc);
        c.add(costactNameField);
       
       gbc.weightx=1.0;
       gbc.gridx=1;
       gbc.gridy=2;
       g1.setConstraints(customerPhoneJlabel,gbc);
       c.add(customerPhoneJlabel);
       
       gbc.weightx=1.0;
       gbc.gridx=1;
       gbc.gridy=3;
       g1.setConstraints(customerPhomefield,gbc);
       c.add(customerPhomefield);
       
       gbc.weightx=1.0;
       gbc.gridx=2;
       gbc.gridy=0;
       g1.setConstraints(contactMobilePhoneJlabel,gbc);
       c.add(contactMobilePhoneJlabel);
       
       gbc.weightx=1.0;
       gbc.gridx=2;
       gbc.gridy=1;
       g1.setConstraints(customerMobiPhonefield,gbc);
       c.add(customerMobiPhonefield);
       
       gbc.weightx=1.0;
       gbc.gridx=2;
       gbc.gridy=2;
       g1.setConstraints(contactEmailJlabel,gbc);
       c.add(contactEmailJlabel);
       
       gbc.weightx=1.0;
       gbc.gridx=2;
       gbc.gridy=3;
       g1.setConstraints(costactEmailField,gbc);
       c.add(costactEmailField);
       
       gbc.weightx=1.0;
       gbc.gridx=3;
       gbc.gridy=0;
       g1.setConstraints(contactFaxJlable,gbc);
       c.add(contactFaxJlable);
       
       gbc.weightx=1.0;
       gbc.gridx=3;
       gbc.gridy=1;
       g1.setConstraints(contactFaxfield,gbc);
       c.add(contactFaxfield);
       
       gbc.weightx=1.0;
       gbc.gridx=3;
       gbc.gridy=2;
       g1.setConstraints(custactpostcodeJlabel,gbc);
       c.add(custactpostcodeJlabel);
       
       gbc.weightx=1.0;
       gbc.gridx=3;
       gbc.gridy=3;
       g1.setConstraints(cunstactPosstcodeField,gbc);
       c.add(cunstactPosstcodeField);
       
       
       gbc.gridx=4;
       gbc.gridy=0;
       gbc.weightx=1.0;
       g1.setConstraints(contactAdressJlabel,gbc);
       c.add(contactAdressJlabel);
       
       gbc.gridx=4;
       gbc.gridy=1;
       gbc.gridwidth=3;
       g1.setConstraints(contactAdressField,gbc);
       c.add(contactAdressField);
       
       
       
       
       
       this.setSize(350,200);
       this.setLocationRelativeTo(null);
      // this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       this.setVisible(true);
       
       
        
       
       
}
 public static void main (String[]args)
    {
     new customerInfor();
    }
}

Answer 1

customerNameJlabel 没有初始化

Answer 2

customerNameJlabel没有初始化，必然NULL pointer

Answer 3

 开发也有几年了，但还没怎么用过swing
  说下空指向的一般解决方法
    首先你找到报错的哪行代码，先看看这行代码中总共有几个对象，然后进行一一排除，如此，就可以解决问题。
  在开发中，空指向是很普遍的问题。
  

Answer 4

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class customerInfor extends JFrame
{
JButton SaveGroupInformationButton,DeleteInfoButton;
JLabel customerIDJlabel,customerNameJlabel,customerPhoneJlabel,
        contactMobilePhoneJlabel,contactNameJlabel,contactEmailJlabel,contactFaxJlable,
        contactAdressJlabel,custactpostcodeJlabel;
    JTextField customerIdField,customerNameField,customerPhomefield,customerMobiPhonefield,
              costactNameField,costactEmailField,contactFaxfield,contactAdressField,cunstactPosstcodeField;GridBagLayout g1;
GridBagConstraints  gbc;
public customerInfor(){
super("客户信息");
Container c=this.getContentPane();
customerIDJlabel=new JLabel("客户 ID");
customerIdField=new JTextField(20);
contactNameJlabel=new JLabel("客户姓名");
customerNameField=new JTextField(20);
customerPhomefield = new JTextField(20);
        contactMobilePhoneJlabel=new JLabel("手机");
        customerMobiPhonefield=new JTextField(20);
        contactNameJlabel=new JLabel("联系人姓名");
        costactNameField=new JTextField(20);
        contactEmailJlabel=new JLabel("E-mail");
        costactEmailField=new JTextField(20);
        contactFaxJlable=new JLabel("传真");
        contactFaxfield=new JTextField(20);
        contactAdressJlabel=new JLabel("联系地址");
        contactAdressField=new JTextField(20);
        custactpostcodeJlabel=new JLabel("邮编");
        cunstactPosstcodeField=new JTextField(20);
customerNameJlabel = new JLabel("你没有初始化");
customerPhoneJlabel = new JLabel("你没有初始化2");
g1=new GridBagLayout();
gbc=new GridBagConstraints();
c.setLayout(g1);//给限定对象gbc的参数赋值       
      // gbc.fill=GridBagConstraints.BOTH;
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=0;
        g1.setConstraints(customerIDJlabel,gbc);
        c.add(customerIDJlabel);
       
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=1;
        g1.setConstraints(customerIdField,gbc);
        c.add(customerIdField);
       
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=3;
        g1.setConstraints(customerNameJlabel,gbc);
        c.add(customerNameJlabel);
       
       
         
        gbc.weightx=1.0;
        gbc.gridx=0;
        gbc.gridy=4;
        g1.setConstraints(customerNameField,gbc);
        c.add(customerNameField);
       
        gbc.weightx=1.0;
        gbc.gridx=1;
        gbc.gridy=0;
        g1.setConstraints(contactNameJlabel,gbc);
        c.add(contactNameJlabel);
       
        gbc.weightx=1.0;
        gbc.gridx=1;
        gbc.gridy=1;
        g1.setConstraints(costactNameField,gbc);
        c.add(costactNameField);
     
      gbc.weightx=1.0;
      gbc.gridx=1;
      gbc.gridy=2;
      g1.setConstraints(customerPhoneJlabel,gbc);
      c.add(customerPhoneJlabel);
     
      gbc.weightx=1.0;
      gbc.gridx=1;
      gbc.gridy=3;
      g1.setConstraints(customerPhomefield,gbc);
      c.add(customerPhomefield);
     
      gbc.weightx=1.0;
      gbc.gridx=2;
      gbc.gridy=0;
      g1.setConstraints(contactMobilePhoneJlabel,gbc);
      c.add(contactMobilePhoneJlabel);
     
      gbc.weightx=1.0;
      gbc.gridx=2;
      gbc.gridy=1;
      g1.setConstraints(customerMobiPhonefield,gbc);
      c.add(customerMobiPhonefield);
     
      gbc.weightx=1.0;
      gbc.gridx=2;
      gbc.gridy=2;
      g1.setConstraints(contactEmailJlabel,gbc);
      c.add(contactEmailJlabel);
     
      gbc.weightx=1.0;
      gbc.gridx=2;
      gbc.gridy=3;
      g1.setConstraints(costactEmailField,gbc);
      c.add(costactEmailField);
     
      gbc.weightx=1.0;
      gbc.gridx=3;
      gbc.gridy=0;
      g1.setConstraints(contactFaxJlable,gbc);
      c.add(contactFaxJlable);
     
      gbc.weightx=1.0;
      gbc.gridx=3;
      gbc.gridy=1;
      g1.setConstraints(contactFaxfield,gbc);
      c.add(contactFaxfield);
     
      gbc.weightx=1.0;
      gbc.gridx=3;
      gbc.gridy=2;
      g1.setConstraints(custactpostcodeJlabel,gbc);
      c.add(custactpostcodeJlabel);
     
      gbc.weightx=1.0;
      gbc.gridx=3;
      gbc.gridy=3;
      g1.setConstraints(cunstactPosstcodeField,gbc);
      c.add(cunstactPosstcodeField);
     
     
      gbc.gridx=4;
      gbc.gridy=0;
      gbc.weightx=1.0;
      g1.setConstraints(contactAdressJlabel,gbc);
      c.add(contactAdressJlabel);
     
      gbc.gridx=4;
      gbc.gridy=1;
      gbc.gridwidth=3;
      g1.setConstraints(contactAdressField,gbc);
      c.add(contactAdressField);
      this.setSize(350,200);
      this.setLocationRelativeTo(null);
      // this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      this.setVisible(true);
     
     
       
     
     
}
public static void main (String[]args)
    {
    new customerInfor();
    }
} 
customerNameJlabel 你没有初始化
customerPhoneJlabel 你没有初始化2
customerPhomefield 没有初始化

Answer 5

上边的代码已经可以运行了   再找bug的时候根据它报错的行号一步步的找 细点心
at customerInfor. <init>(customerInfor.java:60) 错误在60行
    at customerInfor.main(customerInfor.java:172) 

Answer 6

属性中的jlable和jtextfiled都没有实例化所以会报错，
package cn.com.test;import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;public class customerInfor extends JFrame {
JButton SaveGroupInformationButton, DeleteInfoButton; JLabel customerIDJlabel=new JLabel(), customerNameJlabel=new JLabel(), customerPhoneJlabel=new JLabel(),
contactMobilePhoneJlabel=new JLabel(), contactNameJlabel=new JLabel(), contactEmailJlabel=new JLabel(),
contactFaxJlable=new JLabel(), contactAdressJlabel=new JLabel(), custactpostcodeJlabel=new JLabel(); JTextField customerIdField=new JTextField(), customerNameField=new JTextField(), customerPhomefield=new JTextField(),
customerMobiPhonefield=new JTextField(), costactNameField=new JTextField(), costactEmailField=new JTextField(),
contactFaxfield=new JTextField(), contactAdressField=new JTextField(), cunstactPosstcodeField=new JTextField(); GridBagLayout g1; GridBagConstraints gbc; public customerInfor() {
super("客户信息");
Container c = this.getContentPane();
customerIDJlabel = new JLabel("客户 ID");
customerIdField = new JTextField(20);
contactNameJlabel = new JLabel("客户姓名");
customerNameField = new JTextField(20);
contactMobilePhoneJlabel = new JLabel("手机");
customerMobiPhonefield = new JTextField(20);
contactNameJlabel = new JLabel("联系人姓名");
costactNameField = new JTextField(20);
contactEmailJlabel = new JLabel("E-mail");
costactEmailField = new JTextField(20);
contactFaxJlable = new JLabel("传真");
contactFaxfield = new JTextField(20);
contactAdressJlabel = new JLabel("联系地址");
contactAdressField = new JTextField(20);
custactpostcodeJlabel = new JLabel("邮编");
cunstactPosstcodeField = new JTextField(20); g1 = new GridBagLayout();
gbc = new GridBagConstraints();
c.setLayout(g1); //给限定对象gbc的参数赋值  // gbc.fill=GridBagConstraints.BOTH; 
gbc.weightx = 1.0;
gbc.gridx = 0;
gbc.gridy = 0;
g1.setConstraints(customerIDJlabel, gbc);
c.add(customerIDJlabel); gbc.weightx = 1.0;
gbc.gridx = 0;
gbc.gridy = 1;
g1.setConstraints(customerIdField, gbc);
c.add(customerIdField);
gbc.weightx = 1.0;
gbc.gridx = 0;
gbc.gridy = 3;
g1.setConstraints(customerNameJlabel, gbc);
c.add(customerNameJlabel); gbc.weightx = 1.0;
gbc.gridx = 0;
gbc.gridy = 4;
g1.setConstraints(customerNameField, gbc);
c.add(customerNameField); gbc.weightx = 1.0;
gbc.gridx = 1;
gbc.gridy = 0;
g1.setConstraints(contactNameJlabel, gbc);
c.add(contactNameJlabel); gbc.weightx = 1.0;
gbc.gridx = 1;
gbc.gridy = 1;
g1.setConstraints(costactNameField, gbc);
c.add(costactNameField); gbc.weightx = 1.0;
gbc.gridx = 1;
gbc.gridy = 2;
g1.setConstraints(customerPhoneJlabel, gbc);
c.add(customerPhoneJlabel); gbc.weightx = 1.0;
gbc.gridx = 1;
gbc.gridy = 3;
g1.setConstraints(customerPhomefield, gbc);
c.add(customerPhomefield); gbc.weightx = 1.0;
gbc.gridx = 2;
gbc.gridy = 0;
g1.setConstraints(contactMobilePhoneJlabel, gbc);
c.add(contactMobilePhoneJlabel); gbc.weightx = 1.0;
gbc.gridx = 2;
gbc.gridy = 1;
g1.setConstraints(customerMobiPhonefield, gbc);
c.add(customerMobiPhonefield); gbc.weightx = 1.0;
gbc.gridx = 2;
gbc.gridy = 2;
g1.setConstraints(contactEmailJlabel, gbc);
c.add(contactEmailJlabel); gbc.weightx = 1.0;
gbc.gridx = 2;
gbc.gridy = 3;
g1.setConstraints(costactEmailField, gbc);
c.add(costactEmailField); gbc.weightx = 1.0;
gbc.gridx = 3;
gbc.gridy = 0;
g1.setConstraints(contactFaxJlable, gbc);
c.add(contactFaxJlable); gbc.weightx = 1.0;
gbc.gridx = 3;
gbc.gridy = 1;
g1.setConstraints(contactFaxfield, gbc);
c.add(contactFaxfield); gbc.weightx = 1.0;
gbc.gridx = 3;
gbc.gridy = 2;
g1.setConstraints(custactpostcodeJlabel, gbc);
c.add(custactpostcodeJlabel); gbc.weightx = 1.0;
gbc.gridx = 3;
gbc.gridy = 3;
g1.setConstraints(cunstactPosstcodeField, gbc);
c.add(cunstactPosstcodeField); gbc.gridx = 4;
gbc.gridy = 0;
gbc.weightx = 1.0;
g1.setConstraints(contactAdressJlabel, gbc);
c.add(contactAdressJlabel); gbc.gridx = 4;
gbc.gridy = 1;
gbc.gridwidth = 3;
g1.setConstraints(contactAdressField, gbc);
c.add(contactAdressField); this.setSize(350, 200);
this.setLocationRelativeTo(null);
// this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
this.setVisible(true); } public static void main(String[] args) {
new customerInfor();
}
}