Java Enter按钮引发空指针异常

我是Java新手，我遇到了一个空指针异常。我知道它发生在哪里，但无法确定原因。它在下面的代码部分。代码正在验证时间工资以及工资和时间的格式

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javagui.enterButtonActionPerformed(javagui.java:167)
    at javagui$1.actionPerformed(javagui.java:86)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:682)
    at java.awt.EventQueue$3.run(EventQueue.java:680)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:696)
    at java.awt.EventQueue$4.run(EventQueue.java:694)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)

代码如下：-

import java.awt.Component;
import java.text.DecimalFormat;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Andy
 */
public class javagui extends javax.swing.JPanel {


private JLabel tutorTimeLabel;
private JLabel paymentLabel;
private JScrollPane jScrollPane1;
private JTextArea reportTextArea;
private JTextField tutorTime;
private JTextField payment;
private JButton enterButton;
private JButton reportButton;
private JButton quitButton;
private Component paymentText;
private Component tutorTimeText;
//2d array
double[][] timeWage;
//position in array
int timeWageIndex = 0;
//minimum wage
double minimumWage = 6.55;
static final String lineSeparator = System.getProperty("line.separator");







/** Creates new form GUI */
public javagui() {
    initComponents();



}

/** This method is called from within the constructor to
 * initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is
 * always regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {



    tutorTimeLabel = new javax.swing.JLabel();
    paymentLabel = new javax.swing.JLabel();
    jScrollPane1 = new javax.swing.JScrollPane();
    reportTextArea = new javax.swing.JTextArea();
    tutorTimeText = new javax.swing.JTextField();
    paymentText = new javax.swing.JTextField();
    enterButton = new javax.swing.JButton();
    reportButton = new javax.swing.JButton();
    quitButton = new javax.swing.JButton();

    tutorTimeLabel.setText("Enter total tutoring time in minutes:");

    paymentLabel.setText("Enter total amount earned this session:");

    reportTextArea.setColumns(20);
    reportTextArea.setRows(5);
    jScrollPane1.setViewportView(reportTextArea);

    enterButton.setText("Enter");
    enterButton.addActionListener(new java.awt.event.ActionListener() {

        @Override
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            enterButtonActionPerformed(evt);
        }
    });

    reportButton.setText("Report");
    reportButton.addActionListener(new java.awt.event.ActionListener() {
        @Override
    public void actionPerformed(java.awt.event.ActionEvent evt) {
            reportButtonActionPerformed(evt);
        }
    });

    quitButton.setText("Quit");
    quitButton.addActionListener(new java.awt.event.ActionListener() {
        @Override
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            quitButtonActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(23, 23, 23)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 434, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(enterButton, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(reportButton, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(quitButton, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
                .addGroup(layout.createSequentialGroup()
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addComponent(tutorTimeLabel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(paymentLabel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                    .addGap(18, 18, 18)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(paymentText)
                        .addComponent(tutorTimeText, javax.swing.GroupLayout.DEFAULT_SIZE, 120, Short.MAX_VALUE))))
            .addContainerGap(58, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addContainerGap()
                    .addComponent(tutorTimeText, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(layout.createSequentialGroup()
                    .addGap(24, 24, 24)
                    .addComponent(tutorTimeLabel)))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(paymentLabel)
                .addComponent(paymentText, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(enterButton)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(reportButton)
                    .addGap(18, 18, 18)
                    .addComponent(quitButton)
                    .addContainerGap(320, Short.MAX_VALUE))
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 426, Short.MAX_VALUE)))
    );
}// </editor-fold>




public void quitButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
    //select to close the Calculator
    System.exit(0);

}                                          

public void reportButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             
    // TODO add your handling code here:

    reportTextArea.setText(""); // clear previous report
        String newline = "\n";
        double timeTotal = 0;
        double wageTotal = 0;


        //Loops through each entry
        for(int i = 0; i<=timeWageIndex-1; i++){
            //Gets current entry time
            double time = timeWage[i][0];
            //Gets current entry wage
            double wage = timeWage[i][1];
            //Adds to sums
            timeTotal += time;
            wageTotal += wage;

            reportTextArea.append("Minutes = " + time + "    Earnings = $" + wage + newline);
        }

        DecimalFormat df = new DecimalFormat("#.##");
        double average = wageTotal / (timeTotal/60);
        //Displays report
        reportTextArea.append(newline + newline + "*****************************" + newline + newline + newline);
        reportTextArea.append("Report of your wages to Date:" + newline + newline);
        reportTextArea.append("Total Minutes Spent Tutoring = " + timeTotal + newline);
        reportTextArea.append("Total Earnings = $" + wageTotal + newline);
        reportTextArea.append("Average Per Hour Wage = $" + df.format(average) + newline + newline);
        reportTextArea.append("Minimum Wage is currently: $" + minimumWage + newline);

    if(average<minimumWage) {
                    reportTextArea.append("Your average wages are less than average");
                }
        else if(average>minimumWage && average < minimumWage*2.0) {
                    reportTextArea.append("Your average wages are average");
                }
        else if(average >= minimumWage*2.0) {
                    reportTextArea.append("Your average wages are above average");
                }
    }


   public void enterButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
    // TODO add your handling code here:



    //Code Exception error messages when data keyed incorrectly for both textfields
                    double time = 0;
        double wage = 0;


                    //Validates time
        try {
            time = Double.parseDouble(tutorTime.getText());
        } catch (NumberFormatException e1) {
            JOptionPane.showMessageDialog(null, "The time must be a decimal number", "Invalid Input",JOptionPane.ERROR_MESSAGE);
        }

        //Validate wage
        try {
            wage = Double.parseDouble(payment.getText());
        } catch (NumberFormatException e1) {
            JOptionPane.showMessageDialog(null, "The wage must be a decimal number", "Invalid Input",JOptionPane.ERROR_MESSAGE);
        }

        //Time greater than 0 and less than 4 hours
        if(time<=0 || time>240){
            JOptionPane.showMessageDialog(null, "The time must greater than 0 and less than or equal to 4 hours (240 min)", 
                    "Invalid Input",JOptionPane.ERROR_MESSAGE);
        }
        else{
            //Wage greater than 0
            if(wage<=0){
                JOptionPane.showMessageDialog(null, "The wage must greater than 0", 
                        "Invalid Input",JOptionPane.ERROR_MESSAGE);
            }
            else{
                //update array values
                timeWage[timeWageIndex][0] = time;
                timeWage[timeWageIndex][1] = wage;

                //increment index
                timeWageIndex++; 

                //Reset text for user entry
                tutorTime.setText("");
                payment.setText("");
            }
                    } 
   }

导入java.awt.Component；
导入java.text.DecimalFormat；
导入javax.swing.JButton；
导入javax.swing.JLabel；
导入javax.swing.JOptionPane；
导入javax.swing.JScrollPane；
导入javax.swing.JTextArea；
导入javax.swing.JTextField；
/*
*要更改此模板，请选择工具|模板
*然后在编辑器中打开模板。
*/
/**
*
*@作者安迪
*/
公共类javagui扩展了javax.swing.JPanel{
私人JLabel-tutorTimeLabel；
私人JLabel支付标签；
私有JScrollPane jScrollPane1；
私人JTextArea reportTextArea；
私人JTextField tutorTime；
私人领域支付；
私有JButton enterButton；
私有JButton报告按钮；
私有JButton按钮；
私人部分支付文本；
私有组件tutorTimeText；
//二维阵列
双倍【】计时工资；
//阵列中的位置
int-timeWageIndex=0；
//最低工资
双倍最低工资=6.55；
静态最终字符串lineSeparator=System.getProperty（“line.separator”）；
/**创建新表单GUI*/
公共javagui（）{
初始化组件（）；
}
/**此方法从构造函数中调用，以
*初始化表单。
*警告：请勿修改此代码。此方法的内容为
*始终由表单编辑器重新生成。
*/
@抑制警告（“未选中”）
// 
私有组件（）{
tutorTimeLabel=newjavax.swing.JLabel（）；
paymentLabel=newjavax.swing.JLabel（）；
jScrollPane1=newjavax.swing.JScrollPane（）；
reportTextArea=newjavax.swing.JTextArea（）；
tutorTimeText=newjavax.swing.JTextField（）；
paymentText=newjavax.swing.JTextField（）；
enterButton=newjavax.swing.JButton（）；
reportButton=newjavax.swing.JButton（）；
quitButton=newjavax.swing.JButton（）；
setText（“以分钟为单位输入总辅导时间：”；
paymentLabel.setText（“输入本次会话的总收入：”）；
reportTextArea.setColumns（20）；
reportTextArea.setRows（5）；
jScrollPane1.setViewportView（reportTextArea）；
enterButton.setText（“回车”）；
enterButton.addActionListener（新java.awt.event.ActionListener（）{
@凌驾
public void actionPerformed（java.awt.event.ActionEvent evt）{
已执行的EnterButtonAction（evt）；
}
});
reportButton.setText（“报告”）；
reportButton.addActionListener（新java.awt.event.ActionListener（）{
@凌驾
public void actionPerformed（java.awt.event.ActionEvent evt）{
执行的报告按钮（evt）；
}
});
quitButton.setText（“退出”）；
quitButton.addActionListener（新java.awt.event.ActionListener（）{
@凌驾
public void actionPerformed（java.awt.event.ActionEvent evt）{
已执行的退出按钮（evt）；
}
});
javax.swing.GroupLayout=newjavax.swing.GroupLayout（this）；
这个.setLayout（布局）；
layout.setHorizontalGroup(
createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addGap（23,23,23）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addComponent（jScrollPane1，javax.swing.GroupLayout.PREFERRED\u SIZE，434，javax.swing.GroupLayout.PREFERRED\u SIZE）
.addPreferredGap（javax.swing.LayoutStyle.ComponentPlacement.RELATED）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING，false）
.addComponent（enterButton，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u值）
.addComponent（reportButton，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u VALUE）
.addComponent（quitButton，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u VALUE）））
.addGroup（layout.createSequentialGroup（）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.training，false）
.addComponent（tutorimelabel，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u VALUE）
.addComponent（paymentLabel，javax.swing.GroupLayout.DEFAULT_SIZE，javax.swing.GroupLayout.DEFAULT_SIZE，Short.MAX_VALUE））
.addGap（18,18,18）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING，false）
.addComponent（paymentText）
.addComponent（tutorTimeText，javax.swing.GroupLayout.DEFAULT_SIZE，120，Short.MAX_VALUE）））
.addContainerGap（58，简称最大值））
);
layout.setVerticalGroup(
createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（layout.createSequentialGroup（）
.addContainerGap（）
.addComponent（tutorTimeText、javax.swing.GroupLayout.PREFERRED\u SIZE、javax.swing.GroupLayout.DEFAULT\u SIZE、javax.swing.GroupLayout.PREFERRED\u SIZE））
.addGroup（layout.createSequentialGroup（）
.addGap（24,24,24）
.addComponent（tutorTimeLabel）））
.addPreferredGap（javax.swing.LayoutStyle.ComponentPlacement.RELATED）
.addGroup（layout.createParallelGroup（javax.swing.GroupLayout.Alignment.BASELINE）
.addComponent（付款标签）
.addComponent（paymentText，javax.swing.Gro
private JTextField tutorTime;
private JTextField payment;

private Component paymentText;
private Component tutorTimeText;

time = Double.parseDouble(((JTextField) tutorTimeText).getText());