1

第一次在这里海报。我已经走到了尽头，准备放弃我对编程职业的追求。我没有交上我的最后一个作业，因为我无法让我的程序运行。现在，我正在自己做一些额外的练习。一个使用数组的简单练习作业，我无法弄清楚它的最后一点。有人可以告诉我我在这里做错了什么吗？当我运行它时，我可以输入数据，但程序在显示输出之前退出并出现以下错误： 

Exception in thread "main" java.lang.NullPointerException
     at Payroll.getGrossPay(Payroll.java:47)
     at PayrollCalc.main(PayrollCalc.java:32)

我可以分别显示小时数和 payRate，但我不能显示 GrossPay。我对我的构造函数也不满意，但不太确定如何处理它。这个问题需要我初始化 Payroll 类中的数组。

public class Payroll {
    private final int NUM_EMPLOYEES = 3;
    private int[] employeeId = {5658845, 4520125, 7895122}, empId, hours;
    private double[] payRate, wages, grossPay;

    public Payroll()
{
    empId = employeeId;
}
public void setEmployeeId(int[] employeeId)
{
    empId = employeeId;
}
public void setEmpHours(int[] empHoursIn)
{
    hours = empHoursIn;
}
public void setEmpPayRate(double[] empPayRateIn)
{
    payRate = empPayRateIn;
}
public int[] getEmployeeId()
{
    return empId;
}
public int[] getEmpHours()
{
    return hours;
}
public double[] getEmpPayRate()
{
    return payRate;
}
public double[] getGrossPay()
{
    for (int count = 0; count < NUM_EMPLOYEES; count++)
    {
        grossPay[count] = getEmpPayRate()[count] * getEmpHours()[count];
    }

    return grossPay;
}
}

导入 java.util.Scanner；

public class PayrollCalc 
{
public static void main(String[] args) 
{
    int count;
    final int NUM_EMPLOYEES = 3;
    int[] empHours = new int[NUM_EMPLOYEES];
    double[] empPayRate = new double[NUM_EMPLOYEES];
    Scanner keyboard = new Scanner(System.in);
    Payroll payroll = new Payroll();

    for (count = 0; count < NUM_EMPLOYEES; count++)
    {
        System.out.print("Enter total hours for employee " +  
                           payroll.getEmployeeId()[count] + ": ");
        empHours[count] = keyboard.nextInt();
        payroll.setEmpHours(empHours);

        System.out.print("Enter pay rate for employee " + 
                           payroll.getEmployeeId()[count] + ": ");
        empPayRate[count] = keyboard.nextDouble();
        payroll.setEmpPayRate(empPayRate);
    }

    System.out.println("\nEMPLOYEE ID\tGROSS PAY");
    System.out.println("-----------     ---------");

    for (count = 0; count < NUM_EMPLOYEES; count++)
    {
        System.out.println(payroll.getEmployeeId()[count] + "\t\t" + 
                           payroll.getGrossPay()[count]);           
    }
  }
  }

在此先感谢您的帮助！

史蒂夫

4

3 回答 3

1

Your NullPointerException is occuring here:

grossPay[count] = getEmpPayRate()[count] * getEmpHours()[count];

as you haven't initialised the double array grossPay (or payRate or wages). You could use:

private double[] grossPay = new double[NUM_EMPLOYEES];

also you'll need:

private double[] payRate = new double[NUM_EMPLOYEES];
private double[] wages = new double[NUM_EMPLOYEES];
于 2012-10-30T19:34:08.223 回答
1

Doesn't look like you ever initialized the grossPay array - see if this makes a difference:

private double[] payRate, wages;
private double[] grossPay = new double[NUM_EMPLOYEES];

As a tip, when starting out it's probably best to initialize all your variables as soon as you can, which in your case is mostly at construction time. When you get a little more comfortable then you initialize when you need things - for example:

public double[] getGrossPay()
{
  if (grossPay == null) {
    grossPay = new double[NUM_EMPLOYEES]; 

    for (int count = 0; count < NUM_EMPLOYEES; count++)
    {
      grossPay[count] = getEmpPayRate()[count] * getEmpHours()[count];
    }
  }
  return grossPay;
}

Good luck!

于 2012-10-30T19:34:47.223 回答
0

数组 GrossPay 从未在公共 double[] getGrossPay() 中的 Payroll 中初始化。

您需要在使用它之前初始化数组的大小。

可能最好是添加构造函数：

public Payroll() {
grossPay= new double[NUM_EMPLOYEES];
}
于 2012-10-30T19:37:31.650 回答