IComparable与IComparer接口在集合类中的用处

在简单的类型中，我们可以使用CompareTo，与Compare进行比较

例如：

在简单类型中使用

1 int intA = 4;
2  int intB =5;
3 int intResult = intA.CompareTo(intB);
4 Console.WriteLine(intResult);
5 intResult=System.Collections.Comparer.Default.Compare(a,b);
6 Console.WriteLine(intResult);

那么在我们的自定义类型中怎么做呢？

我们通过VS的对象管理器可以知道，我们的CompareTo方法与Compare方法都是IComparable接口和IComparer接口提供的。

如果我们自定义类中实现了这两个接口，那么也可以做这种操作！！！

实现IComparable接口的例子：

实现IComparable接口

 1   class Student : IComparable
 2     {
 3         public int age;
 4         public string name;
 5         public Student()
 6         {
 7         }
 8         public Student(string name, int age)
 9         {
10             this.age = age;
11             this.name = name;
12         }
13         public int CompareTo(object obj)
14         {
15             if (obj is Student)
16             {
17                 Student stu = (Student)obj;
18                 return this.age - stu.age;
19             }
20             else
21             {
22                 throw new Exception("类型不兼容!");
23             }
24         }
25     }
26     class Program
27     {
28         static void Main(string[] args)
29         {
30             Student stu = new Student("秦涛",23);
31             Student stu1 = new Student("王涛",35);
32             if (stu.CompareTo(stu1) > 0)
33             {
34                 Console.WriteLine(stu.name + "年龄大于" + stu1.name + "的年龄");
35             }
36             else if (stu.CompareTo(stu1) == 0)
37             {
38                 Console.WriteLine(stu.name + "年龄等于" + stu1.name + "的年龄");
39             }
40             else
41             {
42                 Console.WriteLine(stu.name + "年龄小于" + stu1.name + "的年龄");
43             }
44         }
45     }

实现IComparer接口的例子：

实现IComparer接口

 1  class StudentDefault:System.Collections.IComparer
 2     {
 3         public static StudentDefault Default = new StudentDefault();
 4         public int Compare(object x, object y)
 5         {
 6             if (x is Student && y is Student)
 7             {
 8                 Student s1 = (Student)x;
 9                 Student s2 = (Student)y;
10                 return s1.age - s2.age;
11             }
12             else
13             {
14                 throw new Exception("类型不兼容");
15             }
16         }
17 
18     }
19 class Program
20     {
21         static void Main(string[] args)
22         {
23             Student stu = new Student("秦涛",23);
24             Student stu1 = new Student("王涛",35);
25           int intResult=  StudentDefault.Default.Compare(stu, stu1);
26           if (intResult > 0)
27           {
28               Console.WriteLine(stu.name + "年龄大于" + stu1.name + "的年龄");
29           }
30           else if (intResult == 0)
31           {
32               Console.WriteLine(stu.name + "年龄等于" + stu1.name + "的年龄");
33           }
34           else
35           {
36               Console.WriteLine(stu.name + "年龄小于" + stu1.name + "的年龄");
37           }
38         }
39     }

有上面的例子可以得出结论如下：

IComparable在要比较的对象的类中实现，可以比较该对象和另一个对象
IComparer在一个单独的类中实现，可以比较任意两个对象。

 class Student : IComparable
    {
        public int age;
        public string name;
        public Student()
        {
        }
        public Student(string name, int age)
        {
            this.age = age;
            this.name = name;
        }
        public int CompareTo(object obj)
        {
            if (obj is Student)
            {
                Student stu = (Student)obj;
                return this.age - stu.age;
            }
            else
            {
                throw new Exception("类型不兼容!");
            }
        }
    }
    class StudentDefault:System.Collections.IComparer
    {
        public static StudentDefault Default = new StudentDefault();
        public int Compare(object x, object y)
        {
            if (x is Student && y is Student)
            {
                Student s1 = (Student)x;
                Student s2 = (Student)y;
                return s1.age - s2.age;
            }
            else
            {
                throw new Exception("类型不兼容");
            }
        }

    }
class Program
    {
        static void Main(string[] args)
        {
            Student stu = new Student("秦涛",23);
            Student stu1 = new Student("王涛",35);
            Student stu2 = new Student("张军", 28);
            ArrayList list = new ArrayList();
            list.Add(stu);
            list.Add(stu1);
            list.Add(stu2);
            foreach (Student var in list)
            {
                Console.WriteLine(var.name + "年龄是" + var.age);
            }
            list.Sort();
            foreach (Student var in list)
            {
                Console.WriteLine(var.name + "年龄是" + var.age);
            }
            list.Sort(StudentDefault.Default);
            foreach (Student var in list)
            {
                Console.WriteLine(var.name + "年龄是" + var.age);
            }
        }
    }

posted on 2011-04-13 16:31 梦里故乡阅读(1139) 评论(4) 编辑收藏举报

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