using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace 专高四 { class 协变 { static void Main_协变() { Stacks<Bear> bears = new Stacks<Bear>(); bears.Push(new Bear()); Stacks<Camal> camals = new Stacks<Camal>(); camals.Push(new Camal()); IStacks<Animal> animal = bears; animal = camals; //Stacks<Bear, Animal> bear = new Stacks<Bear, Animal>(); //IStacks2<Bear, Animal> zoo = bear; } } /*协变:参数传进的是子类,方法返回的是父类,表示父类一定拥有子类的属性,最终一定可以转换*/ /*逆变:参数外部传进的是父类,方法体内用的是子类,表示方法体的子类继承自参数的父类。*/ public interface IStacks<out T1> { T1 Pop(); } public interface IStacks2<in T1, out T2> where T1 : class { T2 Pop(); void Push(T1 obj); } public class Stacks<T1> : IStacks<T1> { T1[] list = new T1[100]; int index; public T1 Pop() { return list[--index]; } public void Push(T1 obj) { list[index++] = obj; } } public class Stacks<T1, T2> : IStacks2<T1, T2> where T1 : class where T2 : class { T2[] list = new T2[100]; int index; public T2 Pop() { return list[--index]; } public void Push(T1 obj) { list[++index] = obj as T2; } } class Animal { } class Bear : Animal { } class Camal : Animal { } }
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace 专高四 { class 泛型 { static void Main() { Stacks<string> s = new Stacks<string>(); s.Push("a"); s.Push("b"); s.Push("c"); Console.WriteLine("{0,-11}{1,-11}{2,-11}", s.Pop(), s.Pop(), s.Pop()); ObjHelper<Student> obj = new ObjHelper<Student>(); Student stu1 = new Student { Id = 1, Name = "xiao" }; var stu2 = obj.Clone(stu1); Console.WriteLine(stu2.Id); } } public class ObjHelper<T> where T : new() { public T Clone(T obj) { T t = new T(); t = obj; return t; } } }