(其中Person是父类，Student和Teacher均继承Person)
package oop;
import oop.demo06.Person;
import oop.demo06.Student;
import oop.demo06.Teacher;
public class Application {
public static void main(String[] args) {
/*
Object > String
Object > Person > Teacher
Object > Person > Student
*/
Object object = new Student();
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);//编译错误
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);//编译错误
//System.out.println(student instanceof String);//编译错误
}
}
类型转换
//把父类转换为子类类，称为向下转型需要强制转换
Person obj = new Student();
//把obj转换为student，即可调用student的方法(假设student有一个go方法
((Studnet) obj).go
//把子类转换为父类，称为向上转型，可能丢失方法
Student student = new Studen();
student.go();
Person person = student
