做企业网站哪家公司专业/精准营销包括哪几个方面

java中，instanceof运算符的前一个操作符是一个引用变量，后一个操作数通常是一个类（可以是接口），用于判断前面的对象是否是后面的类，或者其子类、实现类的实例。如果是返回true，否则返回false。

用法： 
result = object instanceof class 
参数： 
Result：布尔类型。 
Object：必选项。任意对象表达式。 
Class：必选项。任意已定义的对象类。

interface A{ }
class B implements A{ }
class C extends B { }class instanceoftest {public static void main(String[] args){A a=null;B b=null;boolean res;System.out.println("instanceoftest test case 1: ------------------");res = a instanceof A;System.out.println("a instanceof A: " + res);res = b instanceof B;System.out.println("b instanceof B: " + res);a=new B();b=new B();System.out.println("\ninstanceoftest test case 2: ------------------");res = a instanceof A;System.out.println("a instanceof A: " + res);res = a instanceof B;System.out.println("a instanceof B: " + res);res = b instanceof A;System.out.println("b instanceof A: " + res);res = b instanceof B;System.out.println("b instanceof B: " + res);B b2=new C();System.out.println("\ninstanceoftest test case 3: ------------------");res = b2 instanceof A;System.out.println("b2 instanceof A: " + res);res = b2 instanceof B;System.out.println("b2 instanceof B: " + res);res = b2 instanceof C;System.out.println("b2 instanceof C: " + res);}
}
/*result:
instanceoftest test case 1: ------------------
a instanceof A: false
b instanceof B: false
instanceoftest test case 2: ------------------
a instanceof A: true
a instanceof B: true
b instanceof A: true
b instanceof B: true
instanceoftest test case 3: ------------------
b2 instanceof A: true
b2 instanceof B: true
b2 instanceof C: true
*/

//接口Person
public interface Person {public void eat();
}
//实现类People
public class People implements Person {private int a=0;@Overridepublic void eat() {System.out.println("======"+a);}
}
//子类xiaoming：
public class xiaoming extends People {private String name;@Overridepublic void eat() {System.out.println("+++++++++");}
}
//主函数
public static void main(String[] args) {People p=new People();xiaoming x=new xiaoming();System.out.println(p instanceof Person);System.out.println(p instanceof xiaoming); -----2System.out.println(x instanceof Person);System.out.println(x instanceof People);
}
//注意：上面2处的代码在编译时不会报错。
//运行结果：
//true
//false
//true
//true

参考文章：https://www.cnblogs.com/zjxynq/p/5882756.html