java - 在同一类的另一个方法中引用一个方法的输出

Question

这是我的主要方法代码:

public class WeightCalculatorTest {
    public static void main(String[] args) {
        WeightCalculator weCa_init = new WeightCalculator(100);
        weCa_init.displayWeight();
        WeightCalculator weCa_def = new WeightCalculator();
        weCa_def.displayWeight();

        WeightCalculator weCa = new WeightCalculator(123);
        weCa.setWeight();
        weCa.displayWeight();
    }
}

方法如下:

import java.util.Scanner;

public class WeightCalculator {

    private int weight = 0;
    private int hundreds;
    private int fifties;
    private int twenties;
    private int tens;
    private int fives;
    private int ones;
    private int total;
    private int[] result;

    // Default constructor
    public WeightCalculator()
    {

        weight=0;
        System.out.println();
    }   

    // Initial constructor
    public WeightCalculator(int w)
    {

        weight=w;
        System.out.println();
    }

    public void setWeight( ) {
           Scanner keyboard = new Scanner (System.in);
           System.out.println("Life needs a balance");
           System.out.print("How many pounds does the item weight? ");
            weight = keyboard.nextInt();
         }// end inputWeight

        public int[] calculateBalanceWeights() {

            hundreds = weight/100;
            weight %= 100; 

            fifties = weight/50;
            weight %= 50; 

            twenties = weight/20;
            weight %= 20; 

            tens = weight/10;
            weight %= 10; 

            fives = weight/5;
            ones = weight %5;   

            total = hundreds+fifties+twenties+tens+fives+ones;

            int [] result = {hundreds, fifties, twenties, tens, fives, ones, total};

            return result; 

        }// end calcDays


        public void displayWeight() {
            System.out.println("You need "+calculateBalanceWeights()[6]+" weights in total:");
            System.out.println("   "+hundreds +" 100 lbs");
            System.out.println("   "+fifties +"  50 lbs");
            System.out.println("   "+twenties +"  20 lbs");
            System.out.println("   "+tens +"  10 lbs");
            System.out.println("   "+fives +"   5 lbs");
            System.out.println("   "+ones +"   1 lbs");
        }// end of display

}// end of class Time

我的问题在我的代码的这一部分:

System.out.println("You need "+calculateBalanceWeights()[6]+" weights in total:");

为什么如果我引用总计，它不起作用 - 显示 0，而其他变量可以通过名称引用。如果我将 displayWeight 中的其他变量引用为calculateBalanceWeights()[0] 数百，它不起作用？

我真的很困惑其他方法如何存储和引用返回变量？

Aslo 从主方法中我可以打印结果数组

System.out.print(Arrays.toString(weCa.calculateBalanceWeights()));

但是结果与输入的数字错误？

Answer 1

我没发现问题。我猜你的程序运行正常。我运行了你的代码并得到了以下结果。

对于代码的以下部分:

WeightCalculator weCa_init = new WeightCalculator(100);
weCa_init.displayWeight();

程序输出以下内容。

You need 1 weights in total:
   1 100 lbs
   0  50 lbs
   0  20 lbs
   0  10 lbs
   0   5 lbs
   0   1 lbs

由于new WeightCalculator(100)，结果包含1 100 lbs。

对于代码的以下部分:

WeightCalculator weCa_def = new WeightCalculator();
weCa_def.displayWeight();

程序输出以下内容。

You need 0 weights in total:
   0 100 lbs
   0  50 lbs
   0  20 lbs
   0  10 lbs
   0   5 lbs
   0   1 lbs

这次您初始化了没有值的对象 [new WeightCalculator()]。这就是为什么这里一切都为零。

请注意您有两个构造函数，一个带参数，一个不带参数。

对于代码的以下部分:

WeightCalculator weCa = new WeightCalculator(123);
weCa.setWeight();
weCa.displayWeight();

程序输出以下内容。

Life needs a balance
How many pounds does the item weight? 373
You need 8 weights in total:
   3 100 lbs
   1  50 lbs
   1  20 lbs
   0  10 lbs
   0   5 lbs
   3   1 lbs

这次您使用值 [new WeightCalculator(123)] 初始化对象，但在调用 setWeight() 后，程序得到 373 为用户输入并相应地提供输出。

那么，这里发生了什么意想不到的事情呢？

<小时/>

更新

Why if I reference total it does not work - shows 0, while other variables can be referenced by name.

使用时输出为零，

System.out.println("You need "+ total +" weights in total:");

在 displayWeight() 函数内部。

但是当你编写时，你的代码可以正常工作，

System.out.println("You need " + calculateBalanceWeights()[6] + " weights in total:");

这是显而易见的，因为调用函数 calculateBalanceWeights() 会更新所有变量 - 百、五十、二十、十、五、个和总计。

当您仅在 displayWeight() 中使用 total 时，您不会调用 calculateBalanceWeights() 函数。结果，没有变量被更新。

执行以下操作以实现您想要的行为。

public void displayWeight() {
    calculateBalanceWeights();
    System.out.println("You need "+total+ " weights in total:");
    System.out.println("   "+hundreds +" 100 lbs");
    System.out.println("   "+fifties +"  50 lbs");
    System.out.println("   "+twenties +"  20 lbs");
    System.out.println("   "+tens +"  10 lbs");
    System.out.println("   "+fives +"   5 lbs");
    System.out.println("   "+ones +"   1 lbs");
}

此代码片段正确提供了输出。

If I reference for other varibales in displayWeight as calculateBalanceWeights()[0] for hundreds it does not work!

因为你不能多次调用calculateBalanceWeights()。调用calculateBalanceWeights()后，所有参数值(百、五十、二十、十、五、个和总计)都会更新。

因此，只需调用一次 calculateBalanceWeights() 并将返回值保存在变量中，然后用它来打印结果。

Aslo from the main method I can print the result array with System.out.print(Arrays.toString(weCa.calculateBalanceWeights())); But the results are wrong for the number entered?

数字没有错。我查了一下。例如，如果用户提供 373 作为输入，

System.out.print(Arrays.toString(weCa.calculateBalanceWeights()));

打印以下内容。

[3, 1, 1, 0, 0, 3, 8]

只需将其与从 calculateBalanceWeights() 返回的结果进行比较，如下所示。

int [] result = {hundreds, fifties, twenties, tens, fives, ones, total};

希望更新的答案能够解决您的困惑。