Question

我试图从txt文件返回有关基于工资的员工的某些变量，代码将编译但不打印出来。这就是我目前在项目中所做的事情：

public class PayrollPreparation {

    private File source;
    private Scanner input;
    private String payrollType;
    private int employeeID;
    private String employeeName;
    private int hoursWorked;
    private double payRate;
    private double straightPay;

    public void printEmployeeData() {
        System.out.println("Employee ID         Name        Hours Worked        Pay      Amount");

        try {
            source = new File("Payroll.txt");
            input = new Scanner(source);
            input.useDelimiter("[,\n]");
        } catch (Exception e) {
            System.out.println(e);
        }

        while (input.hasNext()) {
            if (payrollType.equals("S")) {
                employeeID = input.nextInt();
                employeeName = input.next();
                hoursWorked = input.nextInt();
                payRate = input.nextDouble();
                payrollType = input.next();
                straightPay = (hoursWorked * payRate);

                System.out.println(" " + employeeID + "           " + employeeName
                        + "                                                "
                        + hoursWorked + "       " + straightPay);

                input.nextLine();
            }
        }
        System.out.println("No More Salaried Employees.");
    }
}

代码全部编译但在测试时if语句出错，并显示java.lang.NullPointerException: null

Answer 1

您的属性payrollType永远不会初始化。

在null对象上调用equals方法时，此结果为NullPointerException。

最佳做法是始终将常量（在您的情况下为字母S）与对象进行比较。

所以你的代码应该是＆＃34; S＆＃34; .equals（payrollType）。

协助空指针异常

1 个答案: