java - 从重写的子类方法调用父类(super class)方法

Question

我确信这有一个简单的解决方案，但我是 Java 新手，无法解决它。

我有一个子类 Payroll，它扩展了父类(super class) Pay，它包含一个名为“calc_payroll”的重写方法。从这个方法中，我想调用同名的父类(super class)方法，并将输出分配给重写方法中的变量。我的代码如下

public class Payroll extends Pay
{
   public double calc_Payroll()
{
    double grossPay = super.calc_Payroll();
    double taxAmt = tax(grossPay);
    double netPay = grossPay - taxAmt;  

    System.out.println(grossPay);

    return netPay;
}


}

下面是父类(super class)中 calc_payroll 方法的代码

public double calc_Payroll()
{
    double otRate = rate * 1.77;
    double otHours = ttlHours - stHours;

    if(stHours == 0)
    {
        grossPay = otHours * rate;
    }

    else
    {
        grossPay = ((stHours * rate) + (otHours * otRate));
    }

    System.out.println(stHours + "//" + otHours + "//" + rate);//for testing

    return grossPay;
}

当从不同的子类调用时，父类(super class)方法可以毫无问题地计算并返回总工资，但是当从具有相同名称的方法调用它时，上面代码中的打印行(我已标记为测试)显示所有变量的零

完整“付费”类别的代码如下所示

public class Pay
{
private double ttlHours;
private int stHours;
private double rate;
double grossPay = 0.0;
final double TAXL = 0.07;
final double TAXM = 0.1;
final double TAXH = 0.16;

public void SetHours(double a)
{
    ttlHours = a;
}

public void SetHoursStr(int a)
{
    stHours = a;
}

public void SetRate(double a)
{
    rate = a;
}

public double GetHours()
{
    return ttlHours;
}

public int GetStHours()
{
    return stHours;
}

public double GetRate()
{
    return rate;
}

public double taxRate()
{
    double taxRate = 0.0;

    if(grossPay <= 399.99)
    {
        taxRate = TAXL;
    }
    else if(grossPay <= 899.99)
    {
        taxRate = TAXM;         
    }
    else
    {
        taxRate = TAXH;
    }

    return taxRate;
}

public double tax(double grossPay)
{
    double ttlTax = 0.0;        

    if(grossPay < 400.00)
    {
        ttlTax += (grossPay * TAXL); 
    }

    else if(grossPay < 900.00)
    {
        ttlTax += (grossPay * TAXM);
    }

    else
    {
        ttlTax += (grossPay * TAXH);
    }

    return ttlTax;
}

public double calc_Payroll()
{
    double otRate = rate * 1.77;
    double otHours = ttlHours - stHours;

    if(stHours == 0)
    {
        grossPay = otHours * rate;
    }

    else
    {
        grossPay = ((stHours * rate) + (otHours * otRate));
    }

    System.out.println(stHours + "//" + otHours + "//" + rate);//for testing

    return grossPay;
}
}

子类 Payroll 不包含其他代码

下面是接受用户输入并为初始化变量赋值的代码

public class CalPayroll extends Pay
{
Payroll nPay = new Payroll();
Accept Read = new Accept(); 


public void AcceptPay()
{
    char select = '0';

    while(select != 'e' && select != 'E')
        {
            System.out.println("Payroll Computation \n");           
            System.out.print("Enter number of hours worked (00.0) <0 for Quick exit>: ");
            SetHours(Read.AcceptInputDouble());
            System.out.print("Enter first number of hours straight (integer or 0 to disable): ");
            SetHoursStr(Read.AcceptInputInt());
            System.out.print("Enter hourly rate of worker (00.00): ");
            SetRate(Read.AcceptInputDouble());
            Screen.ScrollScreen('=', 66, 1);
            Screen.ScrollScreen(1); 
            displayInfo();
            System.out.println("e to exit, any other letter + <Enter> to continue");
            select = Read.AcceptInputChar();
        }
}

public void displayInfo()
{       
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    NumberFormat percent = NumberFormat.getPercentInstance();

    System.out.println("Gross pay is :" + currency.format(calc_Payroll()));
    System.out.println("Tax is :" + percent.format(taxRate()));
    System.out.println("Net pay is :" + currency.format(nPay.calc_Payroll()));      
    Screen.ScrollScreen(1);     
}


}

我很困惑!

Answer 1

从您的代码中可以清楚地看出，ttlHours、stHours 和 Rate 未使用某个合理的值进行初始化。因此，当您仅调用 super.calc_Payroll() 时，将使用 0 或 0.0 等值，正如我在评论中所解释的那样。最好在调用 super.calc_Payroll() 之前先设置这些变量的值。

SetHours(23.4);  //some value

SetHoursStr(5);   //some value

SetRate(2.3);   //some value

此外，您没有 Pay 类的构造函数，请尝试创建它并初始化构造函数中所有未初始化的变量，或使用 setter/getter 方法来设置和获取值。

由于您的两个类都扩展了 Pay 类，因此它会产生您所面临的问题。当您调用 SetHours(Read.AcceptInputDouble()) 时，它设置的是 CalPayroll 从 Pay 继承的变量，而不是 继承的变量>工资单类。您所要做的就是为 Payroll 实例以及当前类设置变量，因为两者都扩展了 Pay。执行以下操作，将 while 循环替换为，

while(select != 'e' && select != 'E')
        {
            System.out.println("Payroll Computation \n");           
            System.out.print("Enter number of hours worked (00.0) <0 for Quick exit>: ");
            SetHours(Read.AcceptInputDouble());
            nPay.SetHours(GetHours());
            System.out.print("Enter first number of hours straight (integer or 0 to disable): ");
            SetHoursStr(Read.AcceptInputInt());
            nPay.SetHoursStr(GetStHours());
            System.out.print("Enter hourly rate of worker (00.00): ");
            SetRate(Read.AcceptInputDouble());
            nPay.SetRate(GetRate());
            Screen.ScrollScreen('=', 66, 1);
            Screen.ScrollScreen(1); 
            displayInfo();
            System.out.println("e to exit, any other letter + <Enter> to continue");
            select = Read.AcceptInputChar();
        }