java 类型判断

//java 类型匹配测试
        Circle circle = new Circle();
        // circle rectangle 实现了 shape
        System.out.println(circle instanceof Circle);//true 关键字
        System.out.println(circle instanceof Shape); //true  对象和类比骄傲
        System.out.println(circle instanceof Rectangle);  //类型不匹配  编译报错
        System.out.println(Shape.class.isAssignableFrom(Rectangle.class));//true 类和类比较
        System.out.println(Shape.class.isInstance(circle));//true 类和对象比较