您的位置：首页 > 运维架构

The Type Comparison Operator instanceof

2011-07-28 16:56 302 查看

This piece of writing is reprinted from the following URL:
http://download.oracle.com/javase/tutorial/java/nutsandbolts/op2.html
The

instanceof

operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.
The following program,

InstanceofDemo

, defines a parent class (named

Parent

), a simple interface (named

MyInterface

), and a child class (named

Child

) that inherits from the parent and implements the interface.

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{}

Output:

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

When using the

instanceof

operator, keep in mind that

null

is not an instance of anything.

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签：

相关文章推荐

新的分享

章节导航