instanceof和類型轉換

package com.Tang.oop.demo06;

public class Application {
    public static void main(String[] args) {
        //Object > String
        //Object > Person > Student
        //Object > Person > Teacher
        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);編譯就報錯
        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);//編譯報錯
        //System.out.println(student instanceof String);//編譯報錯
        /*
            總結：看編譯能否通過主要是看對象左邊的類型與instanceof 右邊的類是否有父子關係
            看運行結果為true或false主要是看對象所指向的引用（右邊的類）與instanceof右邊的類是否存在父子關係
         */
    }
}

package com.Tang.oop.demo06;

public class Application {
    public static void main(String[] args) {
        Person person = new Student();
        //Person相較於Student類是比較高的類，由高到低需要強制轉換
        //也就是將person對象強制轉化為Student類，才能調用go方法
        ((Student)person).go();
        Student student = new Student();
        student.go();
        //由低向高轉則不需要強轉，但是轉化為高之後可能就會丟失一些方法
        Person person1 = student;
        // person1.go();
    }
}

package com.Tang.oop.demo06;

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

package com.Tang.oop.demo06;

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