java中的instanceof的用法

instanceof运算符用法

interface A{

}
class B implements A{

}
class C extends B{

}
public class Iinstanceof {

public static void main(String[] args) {
A ab=new B();
A ac=new C();
B bc=new C();
B bb=new B();
C cc=new C();
//对象实现一个接口，用这个对象和这个接口进行instanceof判断，都为true。
System.out.println("ab instanceof A="+(ab instanceof A));
System.out.println("ac instanceof A="+(ac instanceof A));
System.out.println("bc instanceof A="+(bc instanceof A));
System.out.println("bb instanceof A="+(bb instanceof A));
System.out.println("cc instanceof A="+(cc instanceof A));
//对象和父类进行instanceof判断，都为true
System.out.println("ab instanceof B="+(ab instanceof B));
System.out.println("ac instanceof B="+(ac instanceof B));
System.out.println("bc instanceof B="+(bc instanceof B));
System.out.println("bb instanceof B="+(bb instanceof B));
System.out.println("cc instanceof B="+(cc instanceof B));
//对象和他的子类进行instanceof判断为false
System.out.println("ab instanceof C="+(ab instanceof C));
System.out.println("ac instanceof C="+(ac instanceof C));
System.out.println("bc instanceof C="+(bc instanceof C));
System.out.println("bb instanceof C="+(bb instanceof C));
System.out.println("cc instanceof C="+(cc instanceof C));
}
}

[java] view plain copy
//程序输出：
ab instanceof A=true
ac instanceof A=true
bc instanceof A=true
bb instanceof A=true
cc instanceof A=true
ab instanceof B=true
ac instanceof B=true
bc instanceof B=true
bb instanceof B=true
cc instanceof B=true
ab instanceof C=false
ac instanceof C=true
bc instanceof C=true
bb instanceof C=false
cc instanceof C=true