如何使变量与多种方法一起使用？

Question

由于某种原因，没有计算方法 grossPay() 和 fedTax()。

1. 如何返回grossPay() 结果grosspay？
2. 如何返回fedTax() 结果taxtotal？
3. 我将在哪里计算 totalpay = grosspay - taxtotal？
4. 由于我无法返回taxtotal，我无法判断它是否正常工作，但我是否正确调用grosspay 和dependents 来计算taxtotal？

谢谢！

import java.util.Scanner;

public class WorkPay {

public static void main(String args[]) {
    WorkPay wagecalc = new WorkPay();   // 1. Instantiate the object WorkPay
    WorkPay input = new WorkPay();      // 2. Reference the method to prompt for inputs
    input.prompt4data();
    input.display();                    // 3. Reference the method to display the results
}

public void prompt4data() {
    Scanner console = new Scanner(System.in);
    System.out.println("How many hours have you worked?");
    hours = console.nextDouble();
    System.out.println("What is your wage rate?");
    wage_rate = console.nextDouble();
    System.out.println("How many dependents do you have?");
    dependents = console.nextInt();
}

// private instance variables
    private double hours;
    private double wage_rate;
    private int dependents;
    private double grosspay;
    private double totalpay;
    private double tax;
    private double dependenttax;
    private double taxtotal;

public double grossPay() {
    double total1 = 0;
    double total2 = 0;
    double total3 = 0;
    if (hours <= 40) {
        total1 = wage_rate * hours;
        grosspay = total1;
    }
    else if (hours > 40 && hours <= 60) {
        total2 = total1 + (wage_rate * 1.5) * (hours - 40);
        grosspay = total2;
    }
    else {
        total3 = total2 + (wage_rate * 2) * (hours - 60); 
        grosspay = total3;
    }
    return grosspay;
}

public void fedTax() {
    tax = (0.10 * grosspay);
    dependenttax = (25 * dependents);
    taxtotal = tax + dependenttax;
    if (tax < 0)
        System.out.println("Taxt withheld can't be less than 0.");
}

public void display() {
    System.out.println("The hours worked is: " + hours);
    System.out.println("The hoursly rate is: " + wage_rate);
    System.out.println("The number of dependents is: " + dependents);
    System.out.println("The gross income is: " + grosspay);
    System.out.println("The federal tax withheld is: " + taxtotal);
    System.out.println("The take home pay is: " + totalpay);
}
}

Answer 1

要么调用它们，要么使用getter（更好），getter，又名访问器，是一种命名约定，其中方法以get为前缀（另见Java - Using Accessor and Mutator methods）：

public double getGrossPay() {
    double grosspay = 0; //local now (remove field)
    double total1 = 0;
    double total2 = 0;
    double total3 = 0;
    if (hours <= 40) {
        total1 = wage_rate * hours;
        grosspay = total1;
    }
    else if (hours > 40 && hours <= 60) {
        total2 = total1 + (wage_rate * 1.5) * (hours - 40);
        grosspay = total2;
    }
    else {
        total3 = total2 + (wage_rate * 2) * (hours - 60); 
        grosspay = total3;
    }
    return grosspay;
}

public void display() {
    ...
    System.out.println("The gross income is: " + getGrossPay());
    ...
}

这样总工资总是正确的，没有过时的字​​段。

getGrossPay 还存在一些其他问题，各种小计并未全部计算出来，但我会让你解决这个问题，或者你看看这对你是否有意义：

public double getGrossPay() {
    double grosspay = wage_rate * hours;
    if (hours > 40) grosspay += wage_rate * (hours - 40) * 0.5;
    if (hours > 60) grosspay += wage_rate * (hours - 60) * 0.5;
    return grosspay;
}

Answer 2

让我们从您的领域开始。您只需要其中几个。

// private instance variables
private double hours;
private double wage_rate;
private int dependents;

这三个字段（wage_rate 应该是 wageRate 以符合惯例）是您唯一需要的字段。应计算所有其他值。

接下来，由于您计算的值相互依赖（doubleTime 包括您的基本费率和时间半费率），您应该预先计算这些值。这不应该有任何风险，因为例如，如果您只有 51 小时的工作，您就不会在乎 doubleTime 是否不准确。

public double grossPay() {
    double baseRate = wage_rate * hours;
    double timeAndAHalf = baseRate + (wage_rate * 1.5) * (hours - 40);
    double doubleTime = timeAndAHalf + (wage_rate * 2) * (hours - 60);
    if (hours <= 40) {
        return baseRate;
    } else if (hours > 40 && hours <= 60) {
        return timeAndAHalf;
    } else {
       return doubleTime;
    }
    return grosspay;
}

第三，我们来仔细看看fedTax这个方法。好消息是您不会在其他任何地方使用dependenttax（真的应该是dependentTax）或tax，所以您需要做的就是明确返回 em> 您计算的值。不要忘记实际调用 grossPay 方法，因为您需要将其作为计算的一部分。

public double fedTax() {
    tax = (0.10 * grossPay());
    dependenttax = (25 * dependents);
    return tax + dependenttax;
}

最后，剩下的就是打印您必须在输入字段的最后部分计算的值...

// Method call to...something that does things with gross pay
System.out.println("The gross income is: " + _____);
// Method call to...something that does things with tax...
System.out.println("The federal tax withheld is: " + _____);
// What's the net pay again?
System.out.println("The take home pay is: " + ____);

...但我将那个留给读者作为一个明确的练习。

Answer 3

由于您使用实例变量进行所有计算，因此您不必从方法中返回。您可以继续更新变量并在最后打印它们。

在这里，我对您的程序进行了一些更改。

import java.util.Scanner;

    public class WorkPay {

        // private instance variables
        private double hours;
        private double wage_rate;
        private int dependents;
        private double grosspay;
        private double totalpay;
        private double tax;
        private double dependenttax;
        private double taxtotal;

        public static void main(String args[]) {
            WorkPay input = new WorkPay(); // 2. Reference the method to prompt for
                                           // inputs
            input.prompt4data();
            input.grossPay();
            input.fedTax();
            input.display(); // 3. Reference the method to display the results
        }

        public void prompt4data() {
            Scanner console = new Scanner(System.in);
            System.out.println("How many hours have you worked?");
            hours = console.nextDouble();
            System.out.println("What is your wage rate?");
            wage_rate = console.nextDouble();
            System.out.println("How many dependents do you have?");
            dependents = console.nextInt();
        }

        public void grossPay() {
            double total1 = 0;
            double total2 = 0;
            double total3 = 0;
            if (hours <= 40) {
                total1 = wage_rate * hours;
                grosspay = total1;
            } else if (hours > 40 && hours <= 60) {
                total2 = total1 + (wage_rate * 1.5) * (hours - 40);
                grosspay = total2;
            } else {
                total3 = total2 + (wage_rate * 2) * (hours - 60);
                grosspay = total3;
            }
        }

        public void fedTax() {
            tax = (0.10 * grosspay);
            dependenttax = (25 * dependents);
            taxtotal = tax + dependenttax;
            if (tax < 0)
                System.out.println("Taxt withheld can't be less than 0.");
        }

        public void display() {
            System.out.println("The hours worked is: " + hours);
            System.out.println("The hoursly rate is: " + wage_rate);
            System.out.println("The number of dependents is: " + dependents);
            System.out.println("The gross income is: " + grosspay);
            System.out.println("The federal tax withheld is: " + taxtotal);
            System.out.println("The take home pay is: " + totalpay);
        }
    }