HashMap的常用方法
站在用户的角度思考问题，与客户深入沟通，找到开化网站设计与开化网站推广的解决方案，凭借多年的经验，让设计与互联网技术结合，创造个性化、用户体验好的作品，建站类型包括：成都网站制作、网站建设、企业官网、英文网站、手机端网站、网站推广、域名注册、网站空间、企业邮箱。业务覆盖开化地区。
map的存储和修改方式 map.put(key, value);
map是否包含某个元素map.containsKey(key);
map某个key的value值map.get(key);
参考代码
import java.util.HashMap;
public class BookTest {
static HashMapString, Integer map=new HashMapString, Integer();
static{//初始化图书信息
map.put("三国志", 8);
map.put("红楼梦", 0);
map.put("西游记", 15);
}
public static void main(String[] args) {//main方法
jieShu("水浒");
jieShu("三国志");
huanShu("三国志");
jieShu("红楼梦");
huanShu("红楼梦");
jieShu("红楼梦");
}
public static void jieShu(String name){//借书
if(!map.containsKey(name)){//查询图书馆是否有这本书
System.out.println("书籍："+name+"\t查无此书！");
return;
}
if(map.get(name)=0){//查询图书数量是否为0
System.out.println("书籍："+name+"\t已全部借出，请明日在来");
return;
}
map.put(name, map.get(name)-1);
System.out.println("书籍："+name+"\t借书成功。"+"\t库存："+map.get(name));
}
public static void huanShu(String name){//还书
if(!map.containsKey(name)){
System.out.println("查无此书");
}else{
map.put(name, map.get(name)+1);
System.out.println("书籍："+name+"\t还书成功。"+"\t库存："+map.get(name));
}
}
}
测试输出
书籍：水浒 查无此书！
书籍：三国志 借书成功。 库存：7
书籍：三国志 还书成功。 库存：8
书籍：红楼梦 已全部借出，请明日在来
书籍：红楼梦 还书成功。 库存：1
书籍：红楼梦 借书成功。 库存：0
switch(key){
case 1:
//借书
break;
case 2:
//还书
break;
}
---------------------------------------------------
给你修改了三个地方：
1.borrowBooks方法中，将System.out.println("你要借吗？"); 改为：
System.out.println("你要借吗？输入1表示借，其他数字表示不借。");
保证输入的时候输入的数字，否则会报出异常。
2.borrowBooks方法中，将self[score] = all[9]; 改为：self[score] = all[i];
如果是all[9]，那么就始终是最后一本书籍信息了。
3.have方法中，你是想将所借的书籍信息都打印出来。修改的比较多，下面注释代码是原来的。
void have(Books[] self) {
// for (int i = 0; i 2; i++) {
// self[i].showBookInfo();
// }
for (int i = 0; i 3; i++) {
if(self[i]!=null)
self[i].showBookInfo();
}
}
****************** 附上所有代码：*************************
import java.util.Scanner;
public class TestBook {
public static void main(String[] args) {
Books all[] = new Books[10];
Books self[] = new Books[3];
all[0] = new Books("java", 1, "12345", "tom", 34.0f, "人民出版社");
all[1] = new Books("c", 2, "12346", "tnn", 31.0f, "人民出版社");
all[2] = new Books("c++", 3, "12445", "mm", 35.0f, "人民出版社");
all[3] = new Books("c#", 4, "12365", "tt", 38.0f, "人民出版社");
all[4] = new Books("j2se", 5, "13345", "tosm", 31.1f, "人民出版社");
all[5] = new Books("j2ee", 6, "18345", "ttm", 32.0f, "人民出版社");
all[6] = new Books("jsp", 7, "12335", "cc", 33.0f, "人民出版社");
all[7] = new Books("net", 8, "12341", "bb", 36.0f, "人民出版社");
all[8] = new Books("ip", 9, "12343", "aa", 37.0f, "人民出版社");
all[9] = new Books("tcp", 10, "22345", "jj", 39.0f, "人民出版社");
Readers r = new Readers("xiaoming", 101, "1", 3);
r.searchAllBooks(all);
r.borrowBooks(all, self);
r.have(self);
r.give(all, self);
}
}
class Readers {
Scanner scan = new Scanner(System.in);
String names;
int nums;
String classes;
int grade;
int score = 0;
// Books self[]=new Books[3];
Readers(String n, int u, String c, int g) {
names = n;
nums = u;
classes = c;
grade = g;
}
void searchAllBooks(Books[] all) {// 查书
for (int i = 0; i 10; i++)
all[i].showBookInfo();
// self[score]=all[0];
}
void give(Books[] all, Books[] self) {// 还书
System.out.println("请输入您要还的书的书号");
int n = scan.nextInt();
for (int i = 0; i 10; i++) {
if (n == all[i].num) {
for (int j = 0; j 3; j++) {
if (self[j] == all[i]) {
self[j] = null;
System.out.println("还书成功");
}
}
}
}
}
void have(Books[] self) {
// for (int i = 0; i 2; i++) {
// self[i].showBookInfo();
// }
for (int i = 0; i 3; i++) {
if(self[i]!=null)
self[i].showBookInfo();
}
}
void giveMoney() {
}
void borrowBooks(Books[] all, Books[] self) {
System.out.println("请输入您要查找的书名：");
String n = scan.next();
int i;
for (i = 0; i 10; i++) {
if (n.equals(all[i].name)) {
all[i].showBookInfo();
break;
}
}
//System.out.println("你要借吗？");
System.out.println("你要借吗？输入1表示借，其他数字表示不借。");
int j;
j = scan.nextInt();
if (j == 1) {
System.out.println("借阅成功");
//self[score] = all[9];
self[score] = all[i];
score += 1;
}
if (score 4) {
System.out.println("您还可以借阅" + (3 - score) + "本");
} else {
System.out.println("对不起，一个人只能借3本");
}
}
}
class Books {
String name;
int num;
String ISBN;
String writer;
float price;
String publisher;
Books(String n, int u, String i, String w, float p, String l) {
name = n;
num = u;
ISBN = i;
writer = w;
price = p;
publisher = l;
}
void showBookInfo() {
System.out.println("**************************");
System.out.println("书名：" + name);
System.out.println("索书号：" + num);
System.out.println("ISBN号：" + ISBN);
System.out.println("价格：" + price);
System.out.println("出版社：" + publisher);
System.out.println("**************************");
}
}
----------------------------------------------------
package Management;
import java.util.List;
import java.util.ArrayList;
public class Management {
public static ListBook bookList=null;
public Management() {
// TODO Auto-generated constructor stub
bookList=new ArrayListBook(100);
}
public void addbook(Book book)
{
bookList.add(book);
}
public Book[] findBook(String bookName)
{
Book [] book=new Book[100];
int j=0;
for(int i=0;ibookList.size();i++)
{
if(bookName.equals(bookList.get(i).getName()))
{
book[j]=bookList.get(i);
j++;
}
}
return book;
}
public Book[] ShowAllBook()
{
Book[]book=new Book[100];
for(int i=0;ibookList.size();i++)
{
book[i]=bookList.get(i);
bookList.get(i).printInfo();
}
return book;
}
}
class Book
{
private String name;
private String author;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
void printInfo()
{
System.out.println("书名为"+this.name+"作者为"+this.author);
}
}
class Reader
{
private String name;
public void borrowbook(Book book) {
Management liabry=new Management();
for(int i=0;iliabry.bookList.size();i++)
{ if(book.getAuthor().equals(liabry.bookList.get(i).getAuthor())book.getName().equals(liabry.bookList.get(i).getName()))
{
liabry.bookList.remove(i);
System.out.println("借书成功！");
break;
}
}
}
public void backbook(Book book) {
Management liabry=new Management();
liabry.addbook(book);
System.out.println("还书成功");
}
}
