Java基础重温(八)类型比较操作符--instanceof

    这个"instanceof" 操作符用来拿当前对象与具体的某种类型进行比较。你可以用它来判断某个对象是否为某个class的实例，或者是某个类的子类的实例或一个实现了某一类

接口的类的实例。

    在下面的程序中，InstanceofDemo,定义了一个父类(叫做Parent)，一个简单的接口(MyInterface),一个继承了Parent类并实现了MyInterface接口的子类(Child)。

package com.desmond.test;

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class InstanceofDemo {
    public static void main(String[] args) {

        Parent obj1 = new Parent();
        Parent obj2 = new Child();

        System.out.println("obj1 instanceof Parent: "
            + (obj1 instanceof Parent));
        System.out.println("obj1 instanceof Child: "
            + (obj1 instanceof Child));
        System.out.println("obj1 instanceof MyInterface: "
            + (obj1 instanceof MyInterface));
        System.out.println("obj2 instanceof Parent: "
            + (obj2 instanceof Parent));
        System.out.println("obj2 instanceof Child: "
            + (obj2 instanceof Child));
        System.out.println("obj2 instanceof MyInterface: "
            + (obj2 instanceof MyInterface));
    }
}

class Parent {}
class Child extends Parent implements MyInterface {}
interface MyInterface {}

结果为：

obj1 instanceof Parent: true
obj1 instanceof Child: false
obj1 instanceof MyInterface: false
obj2 instanceof Parent: true
obj2 instanceof Child: true
obj2 instanceof MyInterface: true

来自：http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op2.html