1,新建Application类，作为程序的入口
package oop.demo07;
/*
instanceof 与 类型转换
1,父类引用指向子类对象
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，方便就去的调用，减少重复的代码，
抽象：封装、继承、多态；
*/
public class Application {
public static void main(String[] args) {
// 类型之间的转换 父类 子类
// 高 低
Person s1 = new Student();
// 强制类型转换
Student s2 = (Student) s1;
s2.go();//go
Student s3 = new Student();
s3.go();//go
s3.run();//run
Person s4 = new Student();
s4.run();//run
((Student) s4).go();//go
System.out.println("===================");
Object obj = new Student();
// System.out.println(x instanceof y); //能不能编译通过
System.out.println(obj instanceof Student);//true
System.out.println(obj instanceof Person);//true
System.out.println(obj instanceof Object);//true
System.out.println(obj instanceof Teacher);//false
System.out.println(obj instanceof String);//false
System.out.println("===============");
Person person = new Person();
System.out.println(person instanceof Person);//true
System.out.println(person instanceof Object);//true
System.out.println(person instanceof Student);//false
System.out.println(person instanceof Teacher);//false
// System.out.println(person instanceof String);//编译报错
System.out.println("===============");
Student student = new Student();
System.out.println(student instanceof Person);//true
System.out.println(student instanceof Object);//true
System.out.println(student instanceof Student);//false
// System.out.println(student instanceof Teacher);//编译报错
// System.out.println(student instanceof String);//编译报错
}
}
2,新建Person类
package oop.demo07;
public class Person {
public void run(){
System.out.println("run");
}
}
3,新建Student类
package oop.demo07;
public class Student extends Person {
public void go(){
System.out.println("go");
}
}
4,新建Teacher类
package oop.demo07;
public class Teacher extends Person {
}
5,运行结果
