方法转换（instanceof）oppdemo7

public class Person1 {
    public void run(){
        System.out.println("run");
    }
}

public class Student1 extends Person1{
    public void go(){
        System.out.println("go");
    }
}

public class Application1 {
    public static void main(String[] args) {
        //高               低（低（Student类）到高（Person）可直接转）
        Person1 obj = new Student1();
        //子类转换成父类，可能丢失自己本来的一些方法

        //bjo将这个对象转换为Student1类型，就可以使用Student1类型的方法了
        ((Student1)obj).go();//强制转换（高到低）（父类引用子类方法）
        /*
        Student1 bjo = (Student1) obj;//强制转换（高到低）
        bjo.go();
         */

        /*方法转换
        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
        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

        抽象的三大特性：封装，继承，多态！

         */
    }
}

/*  instanceof 用法：来判断是否可以转型
//System.out.println(X instanceof Y);//能否通过编译通过，就看XY是否有父子（继承）关系

    //Object > String
    //Object > Person1 > Teacher1
    //Object > Person1 > Student1
    Object object = new Student1();
        System.out.println(object instanceof  Student1);//true
                System.out.println(object instanceof  Person1);//true
                System.out.println(object instanceof  Object);//true
                System.out.println(object instanceof  String);//false
                System.out.println(object instanceof  Teacher1);//false
                System.out.println("=============================");

                Person1 person = new Student1();
                System.out.println(person instanceof  Student1);//true
                System.out.println(person instanceof  Person1);//true
                System.out.println(person instanceof  Object);//true
                System.out.println(person instanceof  Teacher1);//false
                //System.out.println(Person1 instanceof  String);//编译报错！！
                System.out.println("=============================");

                Student1 student = new Student1();
                System.out.println(student instanceof  Student1);//true
                System.out.println(student instanceof  Person1);//true
                System.out.println(student instanceof  Object);//true
                //System.out.println(student instanceof  Teacher1);//编译报错
                //System.out.println(Person1 instanceof  String);//编译报错！！
                System.out.println("=============================");

 */