instanceof和类型转换

public class Student extends Person{
    public  void go(){
        System.out.println("go");
    }


}

public class Teacher extends Person{

}

public class Person{
    public void run(){
        System.out.println("sun");
    }
}

/*
  1.父类引用指向子类的对象
  2.把子类转换为父类，向上转型：自动转换
  3.把父类转换为子类，向下转型：强制转换
  4.方便方法的调用，减少重复的代码，简洁

 */
public class Application {
    public static void main(String[] args) {
        //类型之间的转换   父类-->子类    高-->低：强制转换   低-->高：自动转
        Person person = new Student();

        //person将这个对象转换为Student类型，我么就可以使用Student类型的方法了

        ((Student)person).go();
    }
}

/*
        //Object>String
        //Object>Person>Teacher
        //Object>Person>Student

        Object object = new Student();

        //System.out.println(X instanceof Y);能不能通过，看X与Y是否有父子关系

        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);//false
        System.out.println(object instanceof String);//false

        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);//false
        //System.out.println(person instanceof String);  //Person类与String类同级，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);//编译报错
        //System.out.println(student instanceof String);  //编译报错
 */