instanceof和类型转换

instanceof和类型转换

 

 

 

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package base.oop.demo01.demo06;
​
public class Demo01 {
    public static void main(String[] args) {
        //object>string
        //object>person>teacher
        //object>person>student
​
        Object object = new Student();
        //System.out.println(X instanceof Y);能不能编译通过
​
        System.out.println(object instanceof Student);//true
        System.out.println(object instanceof Person);//true
        System.out.println(object instanceof Object);//true
        System.out.println(object instanceof Teacher);//flase
        System.out.println(object instanceof String);//flase
        System.out.println("==================================");
        Person person = new Student();
        System.out.println(person instanceof Student);//true
        System.out.println(person instanceof Person);//true
        System.out.println(person instanceof Object);//true
        System.out.println(person instanceof Teacher);//flase
       // System.out.println(person instanceof String);//编译报错
        System.out.println("=======================");
        Student student = new Student();
        System.out.println(student instanceof Student);//true
        System.out.println(student instanceof Person);//true
        System.out.println(student instanceof Object);//true
        //System.out.println(student instanceof Teacher);//报错
        //System.out.println(student instanceof String);//报错
    }
}

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package base.oop.demo01.demo06;
​
public class Person {
    public void run(){
        System.out.println("run");
    }
​
    }

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package base.oop.demo01.demo06;
​
public class Student extends Person {
    public void go(){
        System.out.println("go");
    }
​
}
​

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package base.oop.demo01.demo06;
​
public class Teacher extends Person {
​
}
​