Question

嘿伙计们我正在为我的Comp Sci 1课程做实验工作，我们正在使用Bluej来学习java。当前的分配是让我们创建一个paystub，其中一些信息是通过键盘输入的，其余的是通过赋值给我们的，我遇到的问题是，虽然代码编译并且没有显示任何当我去测试它时，程序没有运行任何数学运算并将字段留空。我已经尝试了几个小时来解决这个问题，但我完全失败了。以下是我目前所拥有的内容，我非常感谢您对此事的任何建议，非常感谢。

    import java.util.Scanner;
/**
 * Activity1PayStub class is part of Lab 3 and
 * creates a simple pay stub.
 *
 * @author Nicholas Thomas
 * @version 2/6/2018
 */
public class Activity2PayStub
{
    public static final double OVERTIME_FACTOR = 1.5; 
    public static final double SOCIAL_SECURITY_WITHHOLDING = .10;
    public static final double FEDERAL_TAX = .20;
    private String employeeName;
    private String employeeSocialSecurityNumber;
    private int regularHoursWorked;
    private double hourlyPayRate;
    private int overtimeHoursWorked;
    private double regularPay = (hourlyPayRate + regularHoursWorked);
    private double overtimeRate = (OVERTIME_FACTOR * hourlyPayRate);
    private double overtimePay = (overtimeHoursWorked * overtimeRate);
    private double grossPay = (regularPay + overtimePay);
    private double socialSecurityWithholding = (grossPay 
            * SOCIAL_SECURITY_WITHHOLDING);
    private double federalTax = (grossPay - socialSecurityWithholding) 
        * FEDERAL_TAX;
    private double netPay = grossPay - (federalTax + socialSecurityWithholding);
    /**
     * It all starts with the main method.
     *
     * @param args command-line arguments (not used)
     */

    public static void main(String[] args)
    {     
        Scanner keyboard = new Scanner(System.in);
        //Create an Activity2Paystub object
        //a2ps is an Activity2PayStub object
        Activity2PayStub a2ps = new Activity2PayStub();
        //call the methods inside of an Activity2PayStub object
        a2ps.getInput(keyboard);
        a2ps.calculate();
        a2ps.printPayStub();
    }

    /** This is to ensure the keyboard input can be received.
     * Method getInput
     *
     * @param keyboard A parameter
     */
    public void getInput(Scanner keyboard)         
    {
        System.out.print("Employee Name: ");
        employeeName = keyboard.nextLine();
        System.out.print("Social Security Number: ");
        employeeSocialSecurityNumber = keyboard.nextLine();
        System.out.print("Regular Hours Worked: ");       
        regularHoursWorked = keyboard.nextInt();
        System.out.print("Overtime Hours Worked: ");       
        overtimeHoursWorked = keyboard.nextInt();
        System.out.print("Hourly Pay Rate: ");
        hourlyPayRate = keyboard.nextDouble();
    }

    /** Method to do all the math calculations.
     * Method calculate
     *
     */
    public void calculate()
    {
        double regularPay = (hourlyPayRate * regularHoursWorked);
        double overtimeRate = (OVERTIME_FACTOR * hourlyPayRate);
        double overtimePay = (overtimeHoursWorked * overtimeRate);
        double grossPay = (regularPay + overtimePay);
        double socialSecurityWithholding = (grossPay 
                * SOCIAL_SECURITY_WITHHOLDING);
        double federalTax = (grossPay - socialSecurityWithholding) 
            * FEDERAL_TAX;
        double netPay = grossPay - (federalTax + socialSecurityWithholding);
    }

    /** Lets us print and format our stubs.
     * Method printPayStub
     *
     */
    public void printPayStub()
    {
        String format1 = "Name: %-37s SSN: %-11s\n";
        String format2 = "Regular Hours: %-8d Reg Rate: $%-8.2f " 
            + "Reg Pay: $%-8.2f\n";
        String format3 = "Overtime Hours: %-8dOT Rate: $%-8.2f " 
            + " OT Pay: $%-8.2f\n";
        String format4 = "Gross Pay: $%-8.2f\n";
        String format5 = "SS Withholding: $%-8.2f\n";
        String format6 = "Federal Tax: $%-8.2f\n";
        String format7 = "Net Pay: $%-8.2f\n";
        System.out.println("________________________________________"
            + "________________________________________");
        System.out.printf(format1, employeeName, employeeSocialSecurityNumber);
        System.out.printf(format2, regularHoursWorked,
            hourlyPayRate, regularPay);
        System.out.printf(format3, overtimeHoursWorked,  
            overtimeRate, overtimePay);
        System.out.printf(format4, grossPay);
        System.out.printf(format5, socialSecurityWithholding);
        System.out.printf(format6, federalTax);
        System.out.printf(format7, netPay);
        System.out.println("________________________________________"
            + "________________________________________");
    }
}

我目前得到的结果

    ________________________________________________________________________________
Name: Tim Buctoo                            SSN: 111-11-1112
Regular Hours: 40       Reg Rate: $15.50    Reg Pay: $0.00    
Overtime Hours: 15      OT Rate: $0.00      OT Pay: $0.00    
Gross Pay: $0.00    
SS Withholding: $0.00    
Federal Tax: $0.00    
Net Pay: $0.00    
________________________________________________________________________________

Answer 1

当您运行calculate()时，您将引用作用于该方法的变量（例如double regularPay = ...）。确保您正在修改您在班级顶部设置的私有成员变量：

public void calculate() {
    this.regularPay = ...
    //etc.
}

调用double regularPay = ...将为该方法的范围创建一个名为regularPay的新局部变量，一旦该方法终止，对该变量的引用就会丢失。私有成员变量不会被更改，因为它们完全是完全不同的变量。要更改这些内容，您可以使用this.myVariableName引用它们。

Answer 2

声明变量后，不再需要声明它。换句话说，在声明int value;之类的变量之后，现在只需键入value即可使用此变量。请记住像int value = 0;一样初始化它。例如，您在顶部全局声明regularPay，在calculate()本地声明。

<强>范围

范围是可以看到变量的地方。如果在方法之外声明变量，那么您已将整个对象的可见性赋予该变量。如果在方法中声明变量，那么该方法是唯一可以使用该变量的地方。例外情况是返回值。然后可以检索该值，但退出方法后对象本身会丢失。

此关键字

如果在对象中全局声明变量并在方法中使用相同的变量名，则必须指定要引用的变量。然后使用关键字this来指定正在使用的对象内的变量。例如

public class Values{
    //Global in respect to object
    private int value = 0;

    public void setValue(int value) {
        //The variable "value" passed in is local
        this.value = value;
    }
}

如何让Java计算字段？

2 个答案: