//Object > String
//Object > Person > teacher
//Object > Person > Student
Object object = new Student();
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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
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System.out.println("=====================================");
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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); //编译报错
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System.out.println("=====================================");
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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
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//System.out.println(x instanceof y);
// 能不能编译通过，就看x与y是否存在父子关系; 是否为true，看x真相的编译类型是否是Y的子类型
package com.zishi.oop.demo06;
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public class Application {
public static void main(String[] args) {
//类型之间的转换：父 子
//高 //低
Person obj = new Student();
//obj.go(); 无法使用子类里的方法
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//student将这个对象转换为Student类型，我们就可以使用Student类型的方法
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Student student = (Student)obj;
student.go();
//也可以写成： （（Student）obj）.go();
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//子类转换为父类，可能丢失自己本来的一些方法！
Student student1 = new Student();
student1.go();
Person person = student1;
//person.go(); 无法直接调用自己原来的方法
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/*
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
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*/
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}
}