Java中OOP对象和引用

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
}
}