ArrayList排序
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Collections; 6 7 namespace ArrySort 8 { 9 class Program 10 { 11 static void Main(string[] args) 12 { 13 ArrayList arry = new ArrayList() { new Person() { Name = "apple", Age = 12 }, new Person() { Name = "dog", Age = 64 }, new Person() { Name = "cat", Age = 41 } }; 14 Console.WriteLine("排序之前"); 15 for (int i = 0; i < arry.Count; i++) 16 { 17 Console.WriteLine(((Person)arry[i]).Name); 18 } 19 arry.Sort(); 20 Console.WriteLine("排序之后"); 21 for (int i = 0; i < arry.Count; i++) 22 { 23 Console.WriteLine(((Person)arry[i]).Name); 24 } 25 Console.ReadKey(); 26 } 27 28 public class Person : IComparable//实现IComparable接口，则可以调用排序方法Sort()，否则对于有多个参数的对象，Sort()方法不知道该具体比较哪一项 29 { 30 public string Name { get; set; } 31 public int Age { get; set; } 32 33 34 public int CompareTo(object obj)//返回值>0表示比比较对象大,=0跟比较对象相等,<0比比较对象小 35 { 36 Person p = obj as Person;//因为传入的是object类型，所以要将传入的参数转换为需要比较的类型 37 if (p == null) 38 { 39 throw new ArgumentException();//参数无效异常 40 } 41 else 42 { 43 //return this.Age - p.Age;//可以自定义按照类型的某一属性进行比较 44 return this.Name.Length - p.Name.Length; 45 } 46 } 47 } 48 } 49 }
实现IComparable接口，则ArrayList可以调用排序方法Sort()，否则对于有多个参数的对象，Sort()方法不知道该具体比较哪一项
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Collections; 6 7 namespace UseOfICompare 8 { 9 class Program 10 { 11 static void Main(string[] args) 12 { 13 ArrayList array = new ArrayList() {new Person(){Name = "Alice",Age = 42},new Person(){Name = "dog",Age = 62},new Person(){Name = "cat",Age = 15}}; 14 Console.WriteLine("比较前"); 15 for (int i = 0; i < array.Count; i++) 16 { 17 Console.WriteLine(((Person)array[i]).Name); 18 } 19 20 //array.Sort(new CompareByNameLength()); 21 array.Sort(new CompareByAge()); 22 23 Console.WriteLine("比较之后"); 24 for (int i = 0; i < array.Count; i++) 25 { 26 Console.WriteLine(((Person)array[i]).Name); 27 } 28 Console.ReadKey(); 29 } 30 } 31 32 public class Person 33 { 34 public string Name { get; set; } 35 public int Age { get; set; } 36 } 37 38 public class CompareByNameLength : IComparer//实现IComparer接口，其实是做了一个比较器，比较器专门用来比较某一项，将比较器作为参数传入ArrayList的排序Sort()方法就可以实现比较了 39 { 40 public int Compare(object x, object y)//同样返回值是>0,<0,=0 41 { 42 Person p1 = x as Person; 43 Person p2 = y as Person; 44 if (p1 == null && p2 == null) 45 { 46 throw new ArgumentException();//参数类型错误异常 47 } 48 else 49 { 50 return p1.Name.Length - p2.Name.Length;//按姓名长度比较 51 } 52 } 53 } 54 55 public class CompareByAge : IComparer 56 { 57 public int Compare(object x, object y) 58 { 59 Person p1 = x as Person; 60 Person p2 = y as Person; 61 if (p1 == null && p2 == null) 62 { 63 throw new ArgumentException();//参数类型错误 64 } 65 else 66 { 67 return p1.Age - p2.Age; 68 } 69 } 70 } 71 72 }
就一个Person对象来说，如果有两个属性，分别为Name和Age，如果某个时段想用Name长度来作为比较，某个时段想用Age大小来作为比较，如果让Person实现ICompareable接口就不太合适了，因为实现ICompareable接口再调用ArrayList的Sort()方法对按照在比较Person类中定义的规则进行一项的比较。
public int Compare(object x, object y)方法中传入两个对象是内部实现，只需要调用array.sort(new XXXXX());就可以了。
