Question

到目前为止，我已经得到了这个代码，但我正在尝试学习如何完成此方法，以便它将编译所使用的边的总量并在最后一个打印行中打印该值。问题方法是getTotalSides，我目前将它设置为返回0，但我希望它返回总数而不是，意思是：mp1.getSides（）+ mp2.getSides（）+ mp3.getSides（）+ mp4.getSides（）。

public class TestParts {

public static void main(String[] args) {

    MyPolygon mp1 = new MyPolygon();
    MyPolygon mp2 = new MyPolygon(4);
    MyPolygon mp3 = new MyPolygon(5);
    MyPolygon mp4 = new MyPolygon(6);
    System.out.println("Polygon 1 has " + mp1.getSides()
            + " sides, angles total " + mp1.getSumOfAngles());
    System.out.println("Polygon 2 has " + mp2.getSides()
            + " sides, angles total " + mp2.getSumOfAngles());
    System.out.println("Polygon 3 has " + mp3.getSides()
            + " sides, angles total " + mp3.getSumOfAngles());
    System.out.println("Polygon 4 has " + mp4.getSides()
            + " sides, angles total " + mp4.getSumOfAngles());
    System.out.println("There are " + MyPolygon.getTotalSides()
            + " total sides");

}
}

class MyPolygon {
double getSides;

MyPolygon() {
    getSides = 3;
}

static double getTotalSides() {

    return 0;
}

double getSides() {
    // TODO Auto-generated method stub
    return getSides;
}

MyPolygon(double newGetSides) {
    getSides = newGetSides;
}

double getSumOfAngles() {
    return ((getSides - 2) * 180);
}

void setGetSides(double newGetSides) {
    getSides = newGetSides;
}

Answer 1

如果您确实需要一种方法，可以使用varargs（variable arity arguments）来实现此目的：

static double getTotalSides(MyPolygon... polygons) {
  double x = 0;

  for (MyPolygon p: polygons)
  {
   x+= p.getSides();
  }
   return x;
}

然后这样打电话：

System.out.println("There are " + MyPolygon.getTotalSides(mp1,mp2,mp3,mp4)
            + " total sides");

或制作数组

MyPolygon myPolygons = new MyPolygon [4];
myPolygons [0] = mp1;
myPolygons [1] = mp2;
myPolygons [2] = mp3;
myPolygons [3] = mp4;
System.out.println("There are " + MyPolygon.getTotalSides(myPolygons)
            + " total sides");

但是，更好的解决方案是将多边形存储在开头的数组/列表中，然后传递整个数组/将它们列出到方法，执行循环并返回结果。但请注意，列表和数组是不同的，因此，您需要相应地修改方法签名。

Answer 2

为什么不把你写的表达式放在：

System.out.println("There are " + (mp1.getSides() + mp2.getSides() + mp3.getSides() + mp4.getSides()) + " total sides");

由于您尝试将getTotalSides作为类的一部分编写，因此没有一种简单的方法可以检查所有其他实例化对象，并调用它们的方法getSides来添加所有总数。您可以定义一个获取所有多边形对象并添加边的函数，但它不能在类定义下。

Answer 3

您需要查看对象的scope，也许您可以使用某种Collection

public class TestParts {

    public static void main(String[] args) {

        final MyPolygon mp1 = MyPolygon.newInstance(3);
        final MyPolygon mp2 = MyPolygon.newInstance(4);
        final MyPolygon mp3 = MyPolygon.newInstance(5);
        final MyPolygon mp4 = MyPolygon.newInstance(6);
        System.out.println("Polygon 1 has " + mp1.getSides()
                + " sides, angles total " + mp1.getSumOfAngles());
        System.out.println("Polygon 2 has " + mp2.getSides()
                + " sides, angles total " + mp2.getSumOfAngles());
        System.out.println("Polygon 3 has " + mp3.getSides()
                + " sides, angles total " + mp3.getSumOfAngles());
        System.out.println("Polygon 4 has " + mp4.getSides()
                + " sides, angles total " + mp4.getSumOfAngles());
        System.out.println("There are " + MyPolygon.getTotalSides()
                + " total sides");

    }
}

class MyPolygon {

    private static final Collection<MyPolygon> POLYGONS = new LinkedList<MyPolygon>();
    private final double sides;

    private MyPolygon(final double sides) {
        this.sides = sides;
    }

    public static MyPolygon newInstance(final double sides) {
        final MyPolygon polygon = new MyPolygon(sides);
        POLYGONS.add(polygon);
        return polygon;
    }

    public static double getTotalSides() {
        double sides = 0d;
        for (final MyPolygon polygon : POLYGONS) {
            sides += polygon.getSides();
        }
        return sides;
    }

    public double getSides() {
        return sides;
    }

    public double getSumOfAngles() {
        return ((sides - 2) * 180);
    }
}

我已经整理了你的代码，因此它符合命名约定（没有getSides变量）。

Answer 4

如果您想获得有关所有边创建数量的全局信息，请尝试使用静态变量：

class MyPolygon {

    private static int totalSides;
    private int sides;

    MyPolygon() {
        this(3); // constructor chaining: really useful
    }

    MyPolygon(int numSides) {
        this.sides = numSides;
        MyPolygon.totalSides += numSides;
    }

    // ... the rest, incl. getter for sides and static getter for totalSides

}

然而，当你可能不再需要一个多边形时，你必须以某种方式明确地减少数字......

从方法中获取值（java）

4 个答案: