用户定义的非法异常

Question

我有这个程序，如果任何 2 边的总和大于 1，我应该 return 非法三角形异常。我应该把

放在哪里

if(side1 + side2 < side3)
    throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
if(side1 + side3 < side2)
    throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
if(side3 + side2 < side1)
    throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");

在这儿？我不确定把它放在哪里。另外我想知道我写代码的方式是否正确？

class Triangle
{
    public double side1, side2, side3;
    public Triangle() { }
    public Triangle(double s1, double s2, double s3)
    {
        side1 = s1;
        side2 = s2;
        side3 = s3;
    }
    public double Side1
    {
        get { return side1; }
        set {
            if (value<0)
            side1 = value;
        }
    }
    public double Side2
    {
        get { return side2; }
        set {
            if (value < 0)
            side2 = value;
        }
    }
    public double Side3
    {
        get { return side3; }
        set
        {
            if (value < 0)
            side3 = value;
        }
    }
}

class IllegalTriangleException : Exception
{
    public IllegalTriangleException() : base ("Sum of any 2 sides is not greater than the other") { }
    public IllegalTriangleException(string msg) : base("Sum of any 2 sides is not greater than the other" + msg) { }
    public IllegalTriangleException(string msg, Exception innerException) : base("Sum of any 2 sides is not greater than the other" + msg, innerException){ }
}

class Program
{
    static void Main(string[] args)
    {
        try
        {
            Console.WriteLine("Length of side: ");
            double side1 = Convert.ToDouble(Console.ReadLine());
            double side2 = Convert.ToDouble(Console.ReadLine());
            double side3 = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Your triangle is puuuuurfect");
        }
        catch (IllegalTriangleException ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
}

Answer 1

这是我会做的：
通过将字段保持私有，您可以确保仅通过使用适当的属性才能为它们分配任何值。
请注意，构造函数将第一个和第二个值分配给字段，将第三个值分配给属性以检查非法三角形。

public class Triangle
{
    private double _side1, _side2, _side3;
    public Triangle() { }
    public Triangle(double side1, double side2, double side3)
    {
        _side1 = side1;
        _side2 = side2;
        Side3 = side3; // Note: this is calling the property
    }
    public double Side1
    {
        get { return _side1; }
        set {
            if (value > 0) 
            {
            CheckForIllegalTriangle(value, Side2, Side3);
            _side1 = value;
            }
        }
    }
    public double Side2
    {
        get { return _side2; }
        set {
            if (value > 0)
            {
            CheckForIllegalTriangle(Side1, value, Side3);
            _side2 = value;
            }
        }
    }
    public double Side3
    {
        get { return _side3; }
        set
        {
            if (value > 0)
            {
            CheckForIllegalTriangle(Side1, Side2, value);
            _side3 = value;
            }
        }
    }

    private void CheckForIllegalTriangle(double side1, double side2, double side3) {
        if((side1 + side2 < side3) || 
           (side1 + side3 < side2) || 
           (side3 + side2 < side1))
        {
           throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
        }
    }
}

Answer 2

首先。

属性是 public，内部字段应该是私有的。阅读本指南 https://msdn.microsoft.com/en-us/library/x9fsa0sw.aspx?f=255&MSPPError=-2147217396)
您应该首先使用 Triangle(double s1, double s2, double s3) 构造函数创建 Triangle 的实例。在该构造函数中，您可以调用私有 CheckForIllegalTriangle() 来检查边长。如果出现错误，这将抛出异常。
将默认构造函数设为私有。所以你不必担心调用 CheckForIllegalTriangle()。

class Triangle
{
    private double side1, side2, side3;

    private Triangle() { }

    public Triangle(double s1, double s2, double s3)
    {
        side1 = s1;
        side2 = s2;
        side3 = s3;

        CheckForIllegalTriangle();
    }

    public double Side1
    {
        get { return side1; }
        set
        {
            if (value < 0)
                side1 = value;
        }
    }

    public double Side2
    {
        get { return side2; }
        set
        {
            if (value < 0)
                side2 = value;
        }
    }

    public double Side3
    {
        get { return side3; }
        set
        {
            if (value < 0)
                side3 = value;
        }
    }

    public void CheckForIllegalTriangle()
    {
        if ((side1 + side2 < side3) ||
           (side1 + side3 < side2) ||
           (side3 + side2 < side1))
            throw new IllegalTriangleException("Sum of any 2 sides not bigger than the other side");
    }
}


class IllegalTriangleException : Exception
{
    public IllegalTriangleException() : base("Sum of any 2 sides is not greater than the other") { }
    public IllegalTriangleException(string msg) : base("Sum of any 2 sides is not greater than the other" + msg) { }
    public IllegalTriangleException(string msg, Exception innerException) : base("Sum of any 2 sides is not greater than the other" + msg, innerException) { }
}

class Program
{
    static void Main(string[] args)
    {
        try
        {
            Console.WriteLine("Length of side 1: ");
            double side1 = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Length of side 2: ");
            double side2 = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Length of side 3: ");
            double side3 = Convert.ToDouble(Console.ReadLine());
            Triangle t1 = new Triangle(side1, side2, side3);

            Console.WriteLine("Your triangle is puuuuurfect");
        }
        catch (IllegalTriangleException ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
}

Answer 3

不可能每一边都大于另外两边，所以我认为你的问题是错误的。但这是我认为您正在努力实现的目标。

 class Triangle
    {
        public double side1, side2, side3;
        public Triangle() { }
        public Triangle(double s1, double s2, double s3)
        {
            side1 = s1;
            side2 = s2;
            side3 = s3;
            if(side1 + side2 < side3)
               throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
            if(side1 + side3 < side2)
               throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
            if(side3 + side2 < side1)
               throw new illegalTriangleException("Sum of any 2 sides not bigger than the other side");
        }
        public double Side1
        {
            get { return side1; }
            set {
                if (value>0)
                side1 = value;
            }
        }
        public double Side2
        {
            get { return side2; }
            set {
                if (value > 0)
                side2 = value;
            }
        }
        public double Side3
        {
            get { return side3; }
            set
            {
                if (value > 0)
                side3 = value;
            }
        }
    }

    class IllegalTriangleException : Exception
    {
        public IllegalTriangleException(string msg) : base(msg) { }
    }

    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Length of side: ");
                double side1 = Convert.ToDouble(Console.ReadLine());
                double side2 = Convert.ToDouble(Console.ReadLine());
                double side3 = Convert.ToDouble(Console.ReadLine());
                Triangle t = new Triangle(side1, side2, side3);
                Console.WriteLine("Your triangle is puuuuurfect");
            }
            catch (IllegalTriangleException ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }

Answer 4

是具有不变量的可变三角形的良好实现。

但是，这里有一个很好的关于不变性的论据（即没有 setter），否则你最终会遇到从无效状态到有效状态之间转换的问题：

Triangle a(3, 4, 5);
Triangle b(30, 40, 50);

// let's adjust triangle a to match b
try {
    a.Side1 = b.Side1;  // nope
    a.Side2 = b.Side2;
    a.Side3 = b.Side3;
}
catch(IllegalTriangleException e) {
    // darn, we accidentally went through an invalid state of (30, 4, 5)
}

不可变版本更容易实现

class ImmutableTriangle
{
    public ImmutableTriangle(double side1, double side2, double side3)
    {
        if(side1 + side2 <= side3 ||
           side2 + side3 <= side1 ||
           side3 + side1 <= side2)
            throw new IllegalTriangleException("Sum of any 2 sides not bigger than the other side");
        }
        if(side1 <= 0 || side2 <= 0 || side3 <= 0)
            throw new IllegalTriangleException("Sides must be positive");
        }
        Side1 = side1;
        Side2 = side2;
        Side3 = side3;
    }
    public double Side1 { get; private set; }
    public double Side2 { get; private set; }
    public double Side3 { get; private set; }
}

（请注意，我还将 < 换成了 <=，并修复了负长度检查）

用户定义的非法异常

user defined illegal exception

c#

exception

defined