说明：
本系列博客是本人在工作中遇到的一些问题的整理,其中有些资料来源网络博客,有些信息来自出版的书籍,掺杂一些个人的猜想及验证,总结,主要目的是方便知识的查看,并非纯原创。本系列博客会不断更新。原创不容易,支持原创。对于参考的一些其他博客,会尽量把博客地址列在博客的后面,以方便知识的查看。
Class类的isInstance(Object obj)作用与instanceof关键字一样,只不过使用instanceof关键字时,关键字左侧是被检测对象,右侧是类型,isInstance方法的参数是被检测对象
类层次还是一样,使用A、B、C、D,其定义参看上一篇博客。看下如下测试类：
/**
* Created with IntelliJ IDEA.
* User: yejunwu123@gmail.com
* Date: 2014-08-17 20:56
* Description:测试java中Object.class.isInstance()方法
*/
public class IsInstanceTest {
public static void main(String[] args) {
//创建对象
A ab = new B();
A ac = new C();
B bb = new B();
B bc = new C();
C cc = new C();
D dd = new D();
//A.class.isInstance(..)
System.out.println("A.class.isInstance(ab) = " + (A.class.isInstance(ab)));
System.out.println("A.class.isInstance(ac) = " + (A.class.isInstance(ac)));
System.out.println("A.class.isInstance(bb) = " + (A.class.isInstance(bb)));
System.out.println("A.class.isInstance(bc) = " + (A.class.isInstance(bc)));
System.out.println("A.class.isInstance(cc) = " + (A.class.isInstance(cc)));
System.out.println("A.class.isInstance(dd) = " + (A.class.isInstance(dd)));
System.out.println("A.class.isInstance(null) = " + (A.class.isInstance(null)));
System.out.println("-------------------------------------");
//B.class.isInstance(..)
System.out.println("B.class.isInstance(ab) = " + (B.class.isInstance(ab)));
System.out.println("B.class.isInstance(ac) = " + (B.class.isInstance(ac)));
System.out.println("B.class.isInstance(bb) = " + (B.class.isInstance(bb)));
System.out.println("B.class.isInstance(bc) = " + (B.class.isInstance(bc)));
System.out.println("B.class.isInstance(cc) = " + (B.class.isInstance(cc)));
System.out.println("B.class.isInstance(dd) = " + (B.class.isInstance(dd)));
System.out.println("B.class.isInstance(null) = " + (B.class.isInstance(null)));
System.out.println("-------------------------------------");
//C.class.isInstance(..)
System.out.println("C.class.isInstance(ab) = " + (C.class.isInstance(ab)));
System.out.println("C.class.isInstance(ac) = " + (C.class.isInstance(ac)));
System.out.println("C.class.isInstance(bb) = " + (C.class.isInstance(bb)));
System.out.println("C.class.isInstance(bc) = " + (C.class.isInstance(bc)));
System.out.println("C.class.isInstance(cc) = " + (C.class.isInstance(cc)));
System.out.println("C.class.isInstance(dd) = " + (C.class.isInstance(dd)));
System.out.println("C.class.isInstance(null) = " + (C.class.isInstance(null)));
System.out.println("-------------------------------------");
//D.class.isInstance(..)
System.out.println("D.class.isInstance(ab) = " + (D.class.isInstance(ab)));
System.out.println("D.class.isInstance(ac) = " + (D.class.isInstance(ac)));
System.out.println("D.class.isInstance(bb) = " + (D.class.isInstance(bb)));
System.out.println("D.class.isInstance(bc) = " + (D.class.isInstance(bc)));
System.out.println("D.class.isInstance(cc) = " + (D.class.isInstance(cc)));
System.out.println("D.class.isInstance(dd) = " + (D.class.isInstance(dd)));
System.out.println("D.class.isInstance(null) = " + (D.class.isInstance(null)));
}
}
可以看出,即使类D与A、B、C不属于同一个继承层次,编译也会通过,与instanceof不同。
以下是控制台运行结果：
A.class.isInstance(ab) = true
A.class.isInstance(ac) = true
A.class.isInstance(bb) = true
A.class.isInstance(bc) = true
A.class.isInstance(cc) = true
A.class.isInstance(dd) = false
A.class.isInstance(null) = false
-------------------------------------
B.class.isInstance(ab) = true
B.class.isInstance(ac) = true
B.class.isInstance(bb) = true
B.class.isInstance(bc) = true
B.class.isInstance(cc) = true
B.class.isInstance(dd) = false
B.class.isInstance(null) = false
-------------------------------------
C.class.isInstance(ab) = false
C.class.isInstance(ac) = true
C.class.isInstance(bb) = false
C.class.isInstance(bc) = true
C.class.isInstance(cc) = true
C.class.isInstance(dd) = false
C.class.isInstance(null) = false
-------------------------------------
D.class.isInstance(ab) = false
D.class.isInstance(ac) = false
D.class.isInstance(bb) = false
D.class.isInstance(bc) = false
D.class.isInstance(cc) = false
D.class.isInstance(dd) = true
D.class.isInstance(null) = false
不难看出Class类的isInstance(Object obj)作用与instanceof关键字一样。
