例子1
class Interfacedemoplus{
public static void  main(String[] agrs){
	Womanstar Won =new Womanstar();
	//隐式转换
     Whit w = Won;
	 Rich r = Won;
	 //无包含关系,强转
	 Beautiful b = (Beautiful)w;
	 //打印Beau
	 b.Beau();
//小范围 往大范围转
	 WRB wrb =(WRB)b;
	 Whit www =wrb;
    }
}
   //定义接口
   interface Whit{
	   void vertWhit  ();
   }
   interface Rich{
	   void hasmoney  ();
   }
   
   interface Beautiful{
	   void Beau  ();
   }
   //一个接口继承三个接口
   interface WRB extends  Whit,Rich,Beautiful {
	   
   }
   
   //类实现接口多个接口
   class Womanstar implements WRB {
	   public void  vertWhit(){ 
		   System.out.println("很白~~");
	   }
	   public void  hasmoney(){ 
		   System.out.println("有钱~~");
	   }
	   public void  Beau(){ 
		   System.out.println("美丽~~");
	   }
   }
   
   
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例子2
class Interfacedemochangliang{
public static void  main(String[] agrs){
    Jing8 jin8 =new Jing8();
	jin8.meng();
	//变相调用
	Dog d =jin8;
	d.watch();
	//多态
	anmial a = d;
	a.cry();
	//强制转换多态
	Pet pet =(Pet) a;
	//强制转换多态
	anmial aa =(anmial)pet;
	//jin8既继承了dog和anmial又implements Pet所以可以直接看
	Pet jjj =jin8;
    }
}
//接口中加入常量
 abstract class anmial {
	public void cry(){
		 System.out.println("汪汪汪");
	}
}
class Dog extends anmial{
	public void watch(){
		 System.out.println("有人来了~~");
	}
}
	//继承加接口
class Jing8 extends Dog implements Pet {
	public void meng(){
		 System.out.println("!!重新为~~");
	}
}
interface Pet{
	void meng();
}
原文:https://www.cnblogs.com/simly/p/10240248.html