is A和has A的区别

is A	has A
Red is A Color: class Red extends Color{} class Blue extends Color{} class Yellow exrends Color{}	She has A friend： class She{ private Person friend; }
继承关系 （分为： 接口继承——扩展父类类型或功能 略 实现继承——实现公共代码的重用 class Red extends Color{ public void sayHello(){ System.out.print("大家好,"); } } class Red extends Color{ @OverWrite public void sayHello(){ super.sayHello(); System.out.println("我叫red!"); } } class Blue extends Color{ @OverWrite public void sayHello(){ super.sayHello(); System.out.println("我叫blue!"); } }	从属关系