如何在不使用多个返回的情况下返回值

Question

我正在构建一个程序，我们明确不允许在子模块中使用多个返回。

我想知道如何从子模块areaCalc 中传递jimArea、ashtynArea 和steveArea，以便它们可以在主模块中使用。这是我指的子模块，后面是完整的代码。

public static int areaCalc(double depth, double width, double length)
{
 int jimArea = (int)(jimDepth * jimWidth * jimLength);
 int steveArea = (int)(steveDepth * steveWidth * steveLength);
 int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);
}

这是完整的代码。最初我只是返回区域，但事实证明我需要 3 个区域，所以如果不进行多次返回，我不确定如何做到这一点。

import java.util.*;
public class PoolStorageCalculation
{
public static void main(String [] args)
{
 Scanner sc = new Scanner(System.in);
 System.out.println("Please enter the Depth of Steve's Pool in Metres.");
 double steveDepth = sc.nextDouble();
 System.out.println("Please enter the Width of Steve's Pool in Metres.");
 double steveWidth = sc.nextDouble();
 System.out.println("Please enter the Length of Steve's Pool in Metres.");
 double steveLength = sc.nextDouble();
 System.out.println("Please enter the Depth of Jim's Pool in Metres.");
 double jimDepth = sc.nextDouble()
 System.out.println("Please enter the Width of Jim's Pool in Metres.");
 double jimWidth = sc.nextDouble();
 System.out.println("Please enter the Length of Jim's Pool in Metres.");
 double jimLength = sc.nextDouble;
 System.out.println("Please enter the Depth of Ashtyn's Pool in Metres.");
 double ashtynDepth = sc.nextDouble();
 System.out.println("Please enter the Width of Ashtyn's Pool in Metres.");
 double ashtynWidth = sc.nextDouble();
 Systemm.out.println("Please enter the Length of Ashtyn's Pool in Metres.");
 double ashtynLength = sc.nextDouble();
 int area = areaCalc(steveDepth,steveWidth,steveLength,jimDepth,jimWidth,jimLength,ashtynDepth,ashtynLength,ashtynWidth);
 int numRays = rayCalc(steveArea);
 int numSharks = sharkCalc(jimArea);
 int numTurtles = turtleCalc(ashtynArea);
 System.out.println("Steve can store " + numRays + " Sting Rays in his " + steveArea + " Metres Cubed Pool.");
 System.out.println("Jim can store " + numSharks + " Sharks in his " + jimArea + " Metres Cubed Pool.");
 System.out.println("Ashtyn can store " + numTurtles + " Turtles in her " + ashtynArea + " Metres Cubed Pool.");
}
public static int areaCalc(double depth, double width, double length)
{
 int jimArea = (int)(jimDepth * jimWidth * jimLength);
 int steveArea = (int)(steveDepth * steveWidth * steveLength);
 int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);

 return area;
}
public static int rayCalc(int steveArea)
{
 int numRays = (int)(steveArea * 0.5);
 return numRays;
}
public static int sharkCalc(int jimArea)
{
 int numSharks = (int)(jimArea * 0.1);
 return numSharks;
}
public static int turtleCalc(int ashtynArea)
{
 int numTurtles = (int)(ashtynArea * 1.2);
 return numTurtles;
}
}

非常感谢任何帮助，谢谢。 约翰

Answer 1

这里最快的解决方法可能是只返回一个 collection 区域。例如，您可以返回 List<Integer> 而不是单个 int，例如：

public static List<Integer> areaCalc(double depth, double width, double length)
{
    // Note: you don't actually use the method parameters in the assignments below.
    // This is probably a typo.
    int jimArea = (int)(jimDepth * jimWidth * jimLength);
    int steveArea = (int)(steveDepth * steveWidth * steveLength);
    int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);

    List<Integer> areaList = new ArrayList<>();
    areaList.add(jimArea);
    areaList.add(steveArea);
    areaList.add(ashtynArea);

    return areaList;
}

如果你想比这更漂亮，那么你可以考虑创建一个真正的 POJO，它包含三个区域值：

public class AreaClass {
    private int jimArea;
    private int steveArea;
    private int ashtynArea;

    // constructor, getters and setters
}

Answer 2

返回一个对象或数据结构。新程序员倾向于在原语方面考虑太多。您需要将它们组合成对象。

这段代码还能编译吗？

public static int areaCalc(double depth, double width, double length)
{
 int jimArea = (int)(jimDepth * jimWidth * jimLength);
 int steveArea = (int)(steveDepth * steveWidth * steveLength);
 int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);

 return area;
}

jimDepth 和其他定义在哪里？我在您的 main() 方法中看到了它们，但它们都不在 areaCalc() 的范围内。

了解数据结构。像这样：

public class Cube {
    private final double length;
    private final double width;
    private final double depth;

    public Cube(double l, double w, double d) {
        // Question: Do negative or zero dimensions make physical sense?  
        // What would you do about them here?  
        // Hint: Programming by contract and preconditions.
        this.length = l;
        this.width = w;
        this.depth = d;
    }

    public double volume() {
        return this.length*this.width*this.depth;
    }
}

现在您可以为每个人设置不同的套装：

Map<String, Cube> volumes = new HashMap<>();
volumes.put("jim", new Cube(1, 2, 3));
volumes.put("steve", new Cube(4, 5, 6));
volumes.put("ashtyn", new Cube(7, 8, 9));

易于添加更多或按名称查找。

Answer 3

另一种选择是返回一个包含所有值的数组。但我怀疑这会解决你所有的问题，正如 duffymo 在他的回答中指出的那样。

public static int[] areaCalc(double depth, double width, double length)
{
 int jimArea = (int)(jimDepth * jimWidth * jimLength);
 int steveArea = (int)(steveDepth * steveWidth * steveLength);
 int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);
 int[] area = {jimArea,steveArea,ashtynArea};

 return area;
}

Answer 4

解决方案是使用dto - 数据传输对象：类型来包装多个对象：

public static class AreaDto {
    private int jimArea;
    private int steveArea;
    private int ashtynArea;

    public AreaDto(int jimArea, int steveArea, int ashtynArea) {
        this.jimArea = jimArea;
        this.steveArea = steveArea;
        this.ashtynArea = ashtynArea;
    }

    public int getJimArea() {
        return this.jimArea;
    }

    public int getSteveArea() {
        return this.steveArea;
    }

    public int getAshtynArea() {
        return this.ashtynArea;
    }
}

public static AreaDto areaCalc(int steveDepth, int steveWidth, int steveLength, int jimDepth, int jimWidth, int jimLength, int ashtynDepth, int ashtynLength, int ashtynWidth)
{
    int jimArea = (int)(jimDepth * jimWidth * jimLength);
    int steveArea = (int)(steveDepth * steveWidth * steveLength);
    int ashtynArea = (int)(ashtynDepth * ashtynWidth * ashtynLength);

    return new AreaDto(jimArea, steveArea, ashtynArea);
}