By you

多态

什么是多态

  1. 实例方法默认就是多态的
    • 在运行时根据this来决定调用哪个方法
    • 静态方法没有多态
    • 参数静态绑定，接受者动态绑定 多态只对方法的接受者有效 或者说，多态只选择接受者的类型，不选择参数的类型

下面的输出到底是什么？

public class ParamFather {}

public class ParamSon extends ParamFather {}


public class Father{

	public void print(ParamFather param) {
		System.out.println("I am father, param is father.");
	}
	
	public void print(ParamSon param) {
		System.out.println("I am father, param is son.");
	}
}

public class Son extends Father{

	@Override
	public void print(ParamFather param) {
		System.out.println("I am son, param is father.");
	}
	
	@Override
	public void print(ParamSon param) {
		System.out.println("I am son, param is son.");
	}
}

public class Main {

	public static void main(String[] args) {
		
		Father object = new Son();
		ParamFather param = new ParamSon();
		object.print(param);

	}
}

多态实战：策略模式

public class PriceCalculator {

	public int calculate(String strategy, int price, User user) {
	
		switch(strategy) {
			case "no discount":
				return price;
			case "95":
				return (int) (print*0.95);
			case "vip":
				if (user.isVip
			
		}
	}

}

利用策略模式重构

public class PriceCalculator {

	public int calculate(DiscountStrategy strategy, int price, User user) {
	
		return strategy.discount(price, user);
	}

}