Java 获取无法构造的对象数

对于我的一个课堂作业，我需要创建一个创建三角形对象的类。根据几何规则，对于一个有效三角形，任何给定边的长度应小于其他两条边的长度之和。我所编写的对象构造函数类可以采用任意双精度，这意味着可以输入三角形的一侧，其长度比其他两个的总和还要长。这违反了三角形的几何规则（这是可以的）。但是，我想记录有多少三角形违反了几何规则，因此无法构造

通常，您会使用try，catch块来捕获异常。然而，我在这里遇到的问题是，一旦到达异常，就会跳过异常后面的对象，而不会创建该对象。这会导致两个问题：第一，非法对象之后的任何合法对象都不会被创建。第二，除了第一个非法对象之外，我无法跟踪有多少对象未能创建（因为其余对象被跳过）。我如何重新构造代码，以便创建合法对象，即使遇到非法对象，也能记录有多少合法/非法对象？ 我使用了一个自定义异常处理程序对象，它是我为triangle对象编写的，但为了减少代码，这里没有包括它。 我是一个初学者，所以对你来说很明显的解决方案对我来说是模糊的。谢谢你的帮助

这是我的三角形测试仪代码：

public class TestTriangle {

    public static void main(String[] args) throws IllegalTriangleException {
        // Start of try block for creating 4 triangle objects
        try {
            
            Triangle triangle1 = new Triangle();            // create first triangle using default constructor
            System.out.println(triangle1.toString());       // output the information about length of sides
            // output info about perimeter and area of triangle
            System.out.println("The perimeter of the triangle1 is " + triangle1.getPerimeter()); 
            System.out.println("The area of the triangle1 is " + triangle1.getArea());           
            System.out.println();
            
            Triangle triangle2 = new Triangle(3, 4, 5);     // create a second triangle given sides
            System.out.println(triangle2.toString());
            System.out.println("The perimeter of the triangle2 is " + triangle2.getPerimeter());
            System.out.println("The area of the triangle2 is " + triangle2.getArea());
            System.out.println();
            
            Triangle triangle3 = new Triangle(4, 2, 5);     // create a third triangle given sides
            System.out.println(triangle3.toString());
            System.out.println("The perimeter of the triangle3 is " + triangle3.getPerimeter());
            System.out.println("The area of the triangle3 is " + triangle3.getArea());
            System.out.println();
            
            Triangle triangle4 = new Triangle(2, 3, 7);     // try to create an illegal triangle
            System.out.println(triangle4.toString());
            System.out.println("The perimeter of the triangle4 is " + triangle4.getPerimeter());
            System.out.println("The area of the triangle4 is " + triangle4.getArea());
            System.out.println();
            
            Triangle triangle5 = new Triangle(2, 4, 9);     // try to create an illegal triangle
            System.out.println(triangle5.toString());
            System.out.println("The perimeter of the triangle5 is " + triangle5.getPerimeter());
            System.out.println("The area of the triangle5 is " + triangle5.getArea());
            System.out.println();
            
        // catch exceptions, if any 
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }
        System.out.println();
        System.out.println(Triangle.getNumberOfObjects() + " triangles constructed");
        System.out.println(Triangle.illegalAttempts() + " triangle(s) failed to construct");        
    }
}

如果您需要查看，这里是类构造函数：

public class Triangle {
    
    // declare variables for each side of the triangle
    private double side1;
    private double side2;
    private double side3;
    
    // declare variables to keep track of number of objects created or illegal attempts
    private static int numberOfObjects = 0;
    private static int illegalAttempts = 0;
    
    // default constructor for triangle
    public Triangle() {
        side1 = 1.0;
        side2 = 1.0;
        side3 = 1.0;
        numberOfObjects++;
    }
    
    // constructor for creating triangles based on length of sides
    public Triangle(double newSide1, double newSide2, double newSide3) throws IllegalTriangleException {
        setSides (newSide1, newSide2, newSide3);
    
        numberOfObjects++;
    }
    
    // setter for creating triangles given the length of sides
    public void setSides (double newSide1, double newSide2, double newSide3) throws IllegalTriangleException {
        // According to geometric rules, in triangles, any one side should be shorter than the combined length of other two. 
        // Check to see if any one side is longer than the combined length of other two. If so, throw the designed exception.
         
        if (newSide1 >= newSide2 + newSide3) { 
            illegalAttempts++;
            throw new IllegalTriangleException(newSide1, newSide2, newSide3);
            
        } else if (newSide2 >= newSide1 + newSide3) {
            illegalAttempts++;
            throw new IllegalTriangleException(newSide2, newSide1, newSide3);
            
        } else if (newSide3 >= newSide1 + newSide2) {
            illegalAttempts++;
            throw new IllegalTriangleException(newSide3, newSide1, newSide2);
        } else {
            
            side1 = newSide1;       // In case the geometric rule is not violated, create the sides. 
            side2 = newSide2;
            side3 = newSide3;
        }       
    }
    // constructor for getting the number triangle created
    public static int getNumberOfObjects() {
        return numberOfObjects;
    }
    
    public static int illegalAttempts() {
        return illegalAttempts;
    }
    // constructor for calculating the perimeter of triangles 
    public double getPerimeter() {
        return side1 + side2 + side3;
    }
    // constructor for calculating the area of a triangle given three sides: sqrt(p*(p-a)*(p-b)*(p-c))
    public double getArea() {
        double perimeter = side1 + side2 + side3;
        return Math.sqrt(perimeter * (perimeter - side1) * (perimeter - side2) * (perimeter - side3));
    }
    
    // create an string object giving information about the triangle
    public String toString() {
         return "Triangle: Side a = " + side1 + ", Side b = " + side2
                 + ", Side c = " + side3;
    }

}

代码的输出应该是这样的：

三角形：a侧=4.0，b侧=2.0，c侧=5.0 三角形3的周长为11.0 三角形3的面积为64.48255578061404

例外：非法三角形例外：非法三角形，任意两边之和小于另一边 第1面是7.0 第二面是2.0 第三面是3.0

构造了3个三角形 2个三角形构造失败

---

考虑到三角形初始化除了其值之外是相同的，一个选项可能是从try块中提取硬编码的值。如果任何一个三角形未能构造，则将捕获、处理该三角形，然后转到下一个三角形参数集

public class TestTriangle {

    public static void main(String[] args) throws IllegalTriangleException {
        Triangle triangle1 = new Triangle();            // create first triangle using default constructor
        System.out.println(triangle1.toString());       // output the information about length of sides
        // output info about perimeter and area of triangle
        System.out.println("The perimeter of the triangle1 is " + triangle1.getPerimeter());
        System.out.println("The area of the triangle1 is " + triangle1.getArea());
        System.out.println();

        List<List<Integer>> triangleEdgeLengths = new ArrayList<>();
        triangleEdgeLengths.add(Arrays.asList(3, 4, 5));
        triangleEdgeLengths.add(Arrays.asList(4, 2, 5));
        triangleEdgeLengths.add(Arrays.asList(2, 3, 7));
        triangleEdgeLengths.add(Arrays.asList(2, 4, 9));

        triangleEdgeLengths.forEach((edgeLengths) -> {
            try {
                Triangle triangle = new Triangle(edgeLengths.get(0), edgeLengths.get(1), edgeLengths.get(2));
                System.out.println(triangle.toString());
                System.out.println("The perimeter of the triangle is " + triangle.getPerimeter());
                System.out.println("The area of the triangle is " + triangle.getArea());
                System.out.println();
                // catch exceptions, if any
            } catch (IllegalTriangleException ex) {
                System.out.println("Exception: " + ex);
            }
        });

        System.out.println();
        System.out.println(Triangle.getNumberOfObjects() + " triangles constructed");
        System.out.println(Triangle.illegalAttempts() + " triangle(s) failed to construct");
    }
}

twicelost请求了一个避免使用列表的选项。一个有点冗长的选项是将每个三角形构造包装在try/catch中

    public static void main(String[] args) throws IllegalTriangleException {
        Triangle triangle1 = new Triangle();            // create first triangle using default constructor
        System.out.println(triangle1.toString());       // output the information about length of sides
        // output info about perimeter and area of triangle
        System.out.println("The perimeter of the triangle1 is " + triangle1.getPerimeter());
        System.out.println("The area of the triangle1 is " + triangle1.getArea());
        System.out.println();

        try {
            Triangle triangle2 = new Triangle(3, 4, 5);     // create a second triangle given sides
            System.out.println(triangle2.toString());
            System.out.println("The perimeter of the triangle2 is " + triangle2.getPerimeter());
            System.out.println("The area of the triangle2 is " + triangle2.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle3 = new Triangle(4, 2, 5);     // create a third triangle given sides
            System.out.println(triangle3.toString());
            System.out.println("The perimeter of the triangle3 is " + triangle3.getPerimeter());
            System.out.println("The area of the triangle3 is " + triangle3.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle4 = new Triangle(2, 3, 7);     // try to create an illegal triangle
            System.out.println(triangle4.toString());
            System.out.println("The perimeter of the triangle4 is " + triangle4.getPerimeter());
            System.out.println("The area of the triangle4 is " + triangle4.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle5 = new Triangle(2, 4, 9);     // try to create an illegal triangle
            System.out.println(triangle5.toString());
            System.out.println("The perimeter of the triangle5 is " + triangle5.getPerimeter());
            System.out.println("The area of the triangle5 is " + triangle5.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        System.out.println();
        System.out.println(Triangle.getNumberOfObjects() + " triangles constructed");
        System.out.println(Triangle.illegalAttempts() + " triangle(s) failed to construct");
    }

---

这解决了我代码中的问题，我接受答案。谢谢然而，我们仍然不了解列表和数组的列表。我想知道我是否可以用一种更简单的方法得到同样的效果。如需进一步澄清，我们将不胜感激。谢谢。在这种情况下，另一个可能符合您的条件的选项是在每个三角形构造周围复制粘贴try/catch块。我已经更新了我的答案，以包括该选项。

    public static void main(String[] args) throws IllegalTriangleException {
        Triangle triangle1 = new Triangle();            // create first triangle using default constructor
        System.out.println(triangle1.toString());       // output the information about length of sides
        // output info about perimeter and area of triangle
        System.out.println("The perimeter of the triangle1 is " + triangle1.getPerimeter());
        System.out.println("The area of the triangle1 is " + triangle1.getArea());
        System.out.println();

        try {
            Triangle triangle2 = new Triangle(3, 4, 5);     // create a second triangle given sides
            System.out.println(triangle2.toString());
            System.out.println("The perimeter of the triangle2 is " + triangle2.getPerimeter());
            System.out.println("The area of the triangle2 is " + triangle2.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle3 = new Triangle(4, 2, 5);     // create a third triangle given sides
            System.out.println(triangle3.toString());
            System.out.println("The perimeter of the triangle3 is " + triangle3.getPerimeter());
            System.out.println("The area of the triangle3 is " + triangle3.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle4 = new Triangle(2, 3, 7);     // try to create an illegal triangle
            System.out.println(triangle4.toString());
            System.out.println("The perimeter of the triangle4 is " + triangle4.getPerimeter());
            System.out.println("The area of the triangle4 is " + triangle4.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        try {
            Triangle triangle5 = new Triangle(2, 4, 9);     // try to create an illegal triangle
            System.out.println(triangle5.toString());
            System.out.println("The perimeter of the triangle5 is " + triangle5.getPerimeter());
            System.out.println("The area of the triangle5 is " + triangle5.getArea());
            System.out.println();
        } catch (IllegalTriangleException ex) {
            System.out.println("Exception: " + ex);
        }

        System.out.println();
        System.out.println(Triangle.getNumberOfObjects() + " triangles constructed");
        System.out.println(Triangle.illegalAttempts() + " triangle(s) failed to construct");
    }