一、多态性意味着有多重形式。
在面向对象编程范式中,多态性往往表现为"一个接口,多个功能"。
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 6 namespace PolymorphismApplication 7 { 8 /// <summary> 9 /// 几何图形,抽象基类 10 /// </summary> 11 abstract class Geometric 12 { 13 public abstract double Area(); 14 } 15 16 /// <summary> 17 /// 正方形 18 /// </summary> 19 class Square : Geometric 20 { 21 private double side; 22 public Square(double a = 0) 23 { 24 side = a; 25 } 26 public override double Area() 27 { 28 Console.WriteLine("Square 类的面积:"); 29 return (side * side); 30 } 31 } 32 /// <summary> 33 /// 长方形 34 /// </summary> 35 class Rectangle : Geometric 36 { 37 private double length; 38 private double width; 39 public Rectangle(double a = 0, double b = 0) 40 { 41 length = a; 42 width = b; 43 } 44 public override double Area() 45 { 46 Console.WriteLine("Rectangle 类的面积:"); 47 return (width * length); 48 } 49 } 50 /// <summary> 51 /// 圆型 52 /// </summary> 53 class Circle : Geometric 54 { 55 private double r; 56 public Circle(double a = 0) 57 { 58 r = a; 59 } 60 public override double Area() 61 { 62 Console.WriteLine("Circle 类的面积:"); 63 return (3.14*r*r); 64 } 65 } 66 67 class Program 68 { 69 static void Main(string[] args) 70 { 71 Square s = new Square(5); 72 double sa = s.Area(); 73 Console.WriteLine("面积: {0}", sa); 74 Rectangle r = new Rectangle(10, 7); 75 double ra = r.Area(); 76 Console.WriteLine("面积: {0}", ra); 77 Circle c = new Circle(1); 78 double ca = c.Area(); 79 Console.WriteLine("面积: {0}", ca); 80 Console.ReadKey(); 81 } 82 } 83 }
抽象基类Geometric中定义了抽象方法Area public abstract double Area();
不同的子类继承了基类Geometric,分别实现了Area(),但是正方形和长方形和圆型的Area()又不相同。这就是多态性。
二、重载
重载是指具有相同的函数名词,但是参数类型,个数不相同。
举个例子
编程实现两个整数相加
public static int IntPlusInt(int a, int b) { return a + b; }
没有问题,再写个double类型和double类型相加
public static double DoublePlusDouble(double a, double b) { return a + b; }
doub 和int相加:
public static double DoublePlusInt(double a, int b) { return a + b; } public static double IntPlusDouble(int a, double b) { return a + b; }
就这样,简单的int和double类型的相加就需要4个方法。
你在计算时还得想一下,int类型相加的方法名称是什么。
重载,可以使得上面的事情变得简单:
public static int Plus(int a, int b) { return a + b; } public static double Plus(double a, double b) { return a + b; } public static double Plus(double a, int b) { return a + b; } public static double Plus(int a, double b) { return a + b; }
方法名称全都是Plus,不需要起很多名字,方便使用。调用时,vs会根据变量类型自动匹配到相应的方法。
附全部代码
![](https://yqfile.alicdn.com/img_1c53668bcee393edac0d7b3b3daff1ae.gif?x-oss-process=image/resize,w_1400/format,webp)
![](https://yqfile.alicdn.com/img_405b18b4b6584ae338e0f6ecaf736533.gif?x-oss-process=image/resize,w_1400/format,webp)
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 6 namespace Overload 7 { 8 class Program 9 { 10 static void Main(string[] args) 11 { 12 Console.WriteLine("1+2=" + IntPlusInt(1, 2)); 13 Console.WriteLine("1.1+2.2=" + DoublePlusDouble(1.1, 2.2)); 14 Console.WriteLine("1.1+2=" + DoublePlusInt(1.1, 2)); 15 Console.WriteLine("1+2.2=" + IntPlusDouble(1, 2.2)); 16 17 18 Console.WriteLine("1+2=" + Plus(1, 2)); 19 Console.WriteLine("1.1+2.2=" + Plus(1.1, 2.2)); 20 Console.WriteLine("1.1+2=" + Plus(1.1, 2)); 21 Console.WriteLine("1+2.2=" + Plus(1, 2.2)); 22 23 Console.ReadKey(); 24 } 25 26 #region 不使用重载 27 public static int IntPlusInt(int a, int b) 28 { 29 return a + b; 30 } 31 32 public static double DoublePlusDouble(double a, double b) 33 { 34 return a + b; 35 } 36 37 public static double DoublePlusInt(double a, int b) 38 { 39 return a + b; 40 } 41 42 public static double IntPlusDouble(int a, double b) 43 { 44 return a + b; 45 } 46 #endregion 47 48 #region 使用重载 49 public static int Plus(int a, int b) 50 { 51 return a + b; 52 } 53 54 public static double Plus(double a, double b) 55 { 56 return a + b; 57 } 58 59 public static double Plus(double a, int b) 60 { 61 return a + b; 62 } 63 64 public static double Plus(int a, double b) 65 { 66 return a + b; 67 } 68 #endregion 69 } 70 }