Java中OOP对象和引用

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看注释：

class Person2 {    String name;    int score;    String phone;}class App {    public static void main(String[] args) {        int size = 20;        Person p1 = new Person();        Person p2 = new Person();        /*        Person p3 = p1;        p2 = p3;        这三个p1，p2,p3,都只是一个引用类型，只存在两个new出来的对象，而第14行p2指向了第一个引用的        对象后，第二个对象唯一的“线”就“断”了，有Java中的GC（垃圾回收机制）标记，当内存分配给其他不够时        这款内存就会比用掉。比喻：对象为两个空调，而这三个引用类型相当于三个遥控器，连着这两个对象，进行操作。        */        /*对象必须要有引用，一旦没有引用指向，在特定是条件和时机后，就会被...*/        p1.name = "Alice";        p1.score = 98;        p1.phone = "12131";        p2.name = "Bob";        p2.score = 95;        p2.phone = "12134";        Person tmp;        tmp = p1;        tmp.score = 100;        System.out.println(p1.score);//打印100        /*在这里tmp和p1指向的都是一个对象，所以改变tmp的数据对象的值,p1的也同样变了        */       }}

class Person {    String name;    int score;    String phone;    void display() {        System.out.printf("name=%s\tscore=%d\tphone=%s\n",name,score,phone);    }}class App3 {    public static void main(String[] args) {        int size = 20;        Person p1 = new Person();        Person p2 = new Person();        p1.name = "Alice";        p1.score = 98;        p1.phone = "12131";        p2.name = "Bob";        p2.score = 95;        p2.phone = "12134";        Person[] ps = new Person[3];        p1 = new Person();        p1.name = "Alice";        p1.score = 98;        p1.phone = "12131";        ps[0] = p2;        ps[1] = p1;        ps[2] = new Person();        ps[2].name = "Jack";        ps[2].score = 90;        ps[2].phone = "33231";        // ps[1] = new Person();//如果又new了一个，则ps[1]指向的是新的空的才分配出来的一个对象        for(Person person : ps)            person.display();            System.out.println();        for(int i = 0; i < ps.length; i++) {            Person p = ps[i];            p.display();        }        for(int j = 0; j<ps.length-1; j++){        for(int i = 0; i<ps.length-1; i++) {            if(ps[i].score < ps[i+1].score) {                Person t = ps[i];                ps[i] = ps[i+1];                ps[i+1] = t;            }        }       }       System.out.println();       for(Person person : ps)           person.display();           System.out.println();   }}

class Person {    String name;    int score;    String phone;    void display() {        System.out.printf("name=%s\tscore=%d\tphone=%s\n",name,score,phone);    }    String sayHello(String msg) {        return "你好，"+msg+",我是"+name;    }}class App2 {    public static void main(String[] args) {        int size = 20;        Person p1 = new Person();        Person p2 = new Person();        p1.name = "Alice";        p1.score = 98;        p1.phone = "12131";        p2.name = "Bob";        p2.score = 95;        p2.phone = "12134";        p1.display();        p2.display();        System.out.println(p1.sayHello("2017"));        //交换演示//        Person tmp;        tmp = p1;        p1 = p2;        p2 = tmp;        p1.display();        p2.display();       }}

import java.util.Scanner;class Book {    String bookName;    int price;    String writer;  //书名  //价格  //作者  void display() {      System.out.printf("书名：%s\t价格：%d\t作者：%s\n",bookName,price,writer);  }}class BookManage {    static void Bsort(Book[] book ) {        for(int j = 0; j < book.length-1; j++){            for(int i = 0; i < book.length-1; i++) {                if(book[i].price>book[i+1].price) {                    Book tmp = book[i];                    book[i] = book[i+1];                    book[i+1] = tmp;                }            }    }}    public static void main(String[] args) {    int number = 5;        Scanner cin = new Scanner(System.in);        Book[] book = new Book[number];        for(int i = 0; i <number; i++) {            book[i] = new Book();            System.out.println("请输入第"+(i+1)+"本书的名子");            book[i].bookName = cin.next();            System.out.println("请输入第"+(i+1)+"本书的价格");            book[i].price = cin.nextInt();            System.out.println("请输入第"+(i+1)+"本书的作者");            book[i].writer = cin.next();        }        System.out.println();        Bsort(book);        for(Book bookt:book)            bookt.display();        //录入五本书的信息        //按照价格降序排序        //格式化输出信息    }}

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