本文详细介绍了数组的基本概念，包括定义、初始化、使用等步骤，并通过多个案例演示了如何进行数组的遍历、查找、修改、删除及排序等操作，同时讲解了二维数组的应用。
数组
1. 定义
数组就是同一类型的一组数的有序集合，并且个数有限。
2. 定义数组步骤：
-
声明
int[] a;//在栈内存中开辟，用于存放数组在堆内存中的地址 -
开辟空间
a[] = new int[5]; -
赋值
a[1] = 10; -
使用
a[1]+=a[1];
3.案例
-
案例1计算平均分(数组增加)
public static void main(String[] args) { int b[] = new int[] {1,2,3,4,5}; int sum = 0; for(int i = 0; i < b.length;i++) { sum+= b[i]; } System.out.println("平均分是：" + sum/(b.length*1.0)); // int[] a= {1 ,23,54,6,56}; // for(int i = 0;i<a.length;i++) { // System.out.println(a[i]); // } // 声明和初始化必须在一行，否者会报错。 } } -
案例foreach遍历数组
public static void main(String[] args) { Scanner in = new Scanner(System.in); int score[] = new int[5]; int sum = 0; for(int i = 0;i<score.length;i++) { System.out.println("请输入第" + (i+1) + "个同学的分数："); score[i] = in.nextInt(); sum += score[i]; } //foreach或者叫加强for循环 //注意：foreach只能用于数组或集合的遍历 for (int i : score) { System.out.print(" " + i); } double avg = sum/score.length*1.0; System.out.println("五个同学的平均分是：" + avg); } -
案例3通过数组找人(数组查找)
public static void main(String[] args) { Scanner in = new Scanner(System.in); String userName[] = new String[6]; for(int i = 0;i<userName.length;i++) { System.out.println("请输入第" + i + "个姓名："); userName[i] = in.next(); } boolean flag = false; System.out.println("请输入要寻找的姓名："); String findName = in.next(); for(int i = 0;i<userName.length;i++) { if(userName[i].equals(findName)) { flag = true; break; } } if(flag) { System.out.println("找到" + findName); }else { System.out.println("没有找到" + findName); } } -
案例4修改书名(数组修改)
public static void main(String[] args) { Scanner in = new Scanner(System.in); String books[] = new String[4]; System.out.println("请输入书名："); String nowName = in.next(); books[0] = "三国演义"; books[1] = "西游记"; for(int i = 0;i<books.length;i++) { if(books[i] == null) { books[i] = nowName; break; } } System.out.println("*************************"); for (int i =0 ;i<books.length;i++) { if("西游记".equals(books[i])) { books[i] = "东游记"; break; } } for (String book : books) { if(book != null) { System.out.println(book); } } } -
案例5删除书名(数组删除)
Scanner in = new Scanner(System.in); String books[]={"万古神帝","挪威森林","三体","伏天氏"}; boolean isFind = false;//判断是否找到 int index = -1;//找到的电视剧名的索引 for (String book : books) { System.out.print(" " + book); } System.out.println("请输入要删除的书名："); String delBook = in.next(); for(int i = 0;i<books.length;i++) { if(books[i] != null) { if(delBook.equals(books[i])) { index = i; isFind = true; } } } if(isFind) { for(int i = index;i<books.length-1;i++) { books[i] = books[i+1]; } books[books.length-1] = null; System.out.println("\n********************"); for (String book : books) { System.out.print(" "+book); } }else { System.out.println("很遗憾，没有找到"); } } -
案例6比较最大值最小值(数组比较)
public static void main(String[] args) { Scanner in = new Scanner(System.in); int sum = 0; int su[] = new int[6]; for(int i = 0; i < su.length;i++) { System.out.println("请输入第" + (i+1) + "个数："); int score = in.nextInt(); su[i] = score; sum +=su[i]; } int max = su[0]; int min = su[0]; for (int i = 0;i< su.length-1;i++) { if(su[i]>max) { max = su[i]; } } for (int i = 0;i< su.length-1;i++) { if(su[i]<min) { min = su[i]; } } double avg = sum/(su.length*1.0); System.out.println("最大值是：" + max + "\t最小值是" + min + "\t总分是：" + sum + "\t平均分是：" + avg); }
4. 数组排序
-
冒泡排序
public static void main(String[] args) { int array[] = {47,58,96,32,14,45}; for (int i = 0; i < array.length-1; i++) { for (int j = 0; j < array.length-i-1; j++) { if (array[j]<array[j+1]) { int temp = array[j]; array[j] = array[j+1]; array[j+1] = temp; } } } for (int a : array) { System.out.print(" " + a); } } -
其他排序
-
i++和++i的区别
-
i++先计算后自增
int a=10; int b = a+++5; System.out.println("a="+a); System.out.println("b="+a); 结果 a=11 b=15 -
++i先自增后计算
int a=10; int b = ++a+5; System.out.println("a="+a); System.out.println("b="+a); 结果 a=11 b=16
-
5.二维数组和二重循环
-
定义二维数组
Scanner in = new Scanner(System.in); //定义二维数组 int score[][] = new int[3][4]; for (int i = 0; i < score.length;i ++) { System.out.println("****************第" + (i+1) + "班*************************"); int sum = 0; for (int j= 0; j < score[i].length; j++) { System.out.print("第" + (i+1) +"班第" + (j+1) + "个同学的分数::"); score[i][j] = in.nextInt(); sum += score[i][j]; } double avg = sum/(score[i].length*1.0); System.out.println("第" + (i+1) + "班的平均分:" + avg); } for (int i = 0; i < score.length; i++) { for (int j = 0; j < score[i].length; j++) { System.out.println(score[i][j]); } } -
应用
Scanner in = new Scanner(System.in); //定义二维数组 int score[][] = new int[3][4]; for (int i = 0; i < score.length;i ++) { for (int j= 0; j < score[i].length; j++) { System.out.print("第" + (i+1) +"班第" + (j+1) + "个同学的分数:"); score[i][j] = in.nextInt(); } } int count = 0; for (int i = 0; i < score.length; i++) { for (int j = 0; j < score[i].length; j++) { if(score[i][j]>80) { count++; } } } System.out.println("大于80分的有" +count+"人"); } -
案例
Scanner in = new Scanner(System.in); //判断是否买了衣服 String pan = ""; //记录买了多少件 int count = 0; //记录一家店买了多少件衣服 int s = 0; for (int i = 1; i <= 5; i++) { System.out.println("欢迎光临第" + i + "家专卖店"); do { System.out.print("要离开吗（y/n）?"); pan = in.next(); if("n".equals(pan)) { System.out.println("买了一件衣服！"); count++; s++; } } while ("n".equals(pan)&& s<3); System.out.println("离店结账"); System.out.println(); } System.out.println("总共买了" + count + "件衣服"); } -
99乘法表
for (int i = 1; i <= 9; i++) { for (int j = 1; j <= i; j++) { System.out.print(j + "*" + i + "=" + (i*j) + "\t"); } System.out.println(); }
6.练习1
Scanner in = new Scanner(System.in);
String DVDName[] = new String[100];//存储DVD名字
int sta[] = new int[100];//记录DVD状态0表示借出，1表示可借
String DVDData[] = new String[100];//记录DVD借出时间
//DVD原始数据
DVDName[0] = "英雄本色";
sta[0] = 0;
DVDData[0] = "2020-08-12";
DVDName[1] = "三国演义";
sta[1] = 1;
DVDData[1] = "";
DVDName[2] = "穿越火线";
sta[2] = 0;
DVDData[2] = "2020-08-01";
DVDName[3] = "二十不惑";
sta[3] = 1;
DVDData[3] = "";
int an=0;
do {
System.out.println("欢 迎 使 用 迷 你 DVD 管 理 器");
System.out.println("-------------------------------------");
System.out.println("1. 新 增 DVD");
System.out.println("2. 查 看 DVD");
System.out.println("3. 删 除 DVD");
System.out.println("4. 借 出 DVD");
System.out.println("5. 归 还 DVD");
System.out.println("6. 退 出 ");
System.out.print("--------------------------------------\n");
System.out.print("请选择： ");
int choice = in.nextInt();
switch (choice) {
case 1:
System.out.println("---> 新 增 DVD\n");
for (int i = 0; i < DVDName.length; i++) {
if(DVDName[i] == null) {
System.out.print("请输入DVD名称：");
DVDName[i] = in.next();
sta[i] = 1;
System.out.println("新增《" + DVDName[i] + "》成功!");
System.out.println("**********************");
break;
}
}
System.out.print("输入0返回:");
an = in.nextInt();
if(an != 0) {
System.out.println("输入错误请重新输入：");
an=0;
}
break;
case 2:
System.out.println("---> 查看 DVD\n");
System.out.println("序号\t状态\t名称\t借出日期");
for (int i = 0; i < DVDName.length; i++) {
if(DVDName[i] !=null) {
if(sta[i] ==0) {
System.out.println((i+1) + "\t借出\t" + DVDName[i] + "\t" + DVDData[i]);
}else {
System.out.println((i+1) + "\t可借\t" + DVDName[i] + "\t" + DVDData[i]);
}
}
}
System.out.print("输入0返回:");
an = in.nextInt();
if(an != 0) {
System.out.println("输入错误请重新输入：");
an=0;
}
break;
case 3:
System.out.println("---> 删除 DVD\n");
boolean falg = true;
do {
int index=0;
System.out.print("请输入DVD名称：");
String delDVD = in.next();
for (int i = 0; i < DVDName.length-1; i++) {
if(delDVD.equals(DVDName[i])&&DVDName != null) {
if(sta[i] == 1) {
index = i;
falg = false;
while (DVDName[index+1] != null) {
DVDName[index] = DVDName[index+1];
sta[index] = sta[index+1];
DVDData[index] = DVDData[index+1];
}
DVDName[i] = null;
System.out.println("删除《" + delDVD + "》成功");
}else {
System.out.println("已借出，不能删除");
}
}
}
if(falg) {
System.out.println("没有找到匹配信息!");
System.out.println("**************************");
break;
}
} while (falg);
System.out.print("输入0返回:");
an = in.nextInt();
if(an != 0) {
System.out.println("输入错误请重新输入：");
an=0;
}
break;
case 4:
System.out.println("---> 借出DVD\n");
System.out.print("请输入DVD名称：");
String selDVD = in.next();
falg =true;
for (int i = 0; i < DVDName.length; i++) {
if(selDVD.equals(DVDName[i])&&DVDName[i]!=null) {
if (sta[i] ==1) {
sta[i] = 0;
falg = false;
System.out.println("请输入借出日期（年-月-日）:");
DVDData[i] = in.next();
}else {
System.out.println("DVD已借出");
break;
}
}
}
if(falg){
System.out.println("没有该DVD");
break;
}else {
System.out.println("借出成功！");
}
System.out.print("输入0返回:");
an = in.nextInt();
if(an != 0) {
System.out.println("输入错误请重新输入：");
an=0;
}
break;
case 5:
System.out.println("---> 归还DVD\n");
System.out.print("请输入DVD名称：");
String inDVD = in.next();
for (int i = 0; i < DVDName.length; i++) {
if(inDVD.equals(DVDName[i])&&DVDName[i]!=null&&sta[i] == 0) {
sta[i] = 1;
System.out.println("请输入借出日期（年-月-日）:");
DVDData[i] = in.next();
}
}
System.out.println("\n谢谢使用");
System.out.print("输入0返回:");
an = in.nextInt();
if(an != 0) {
System.out.println("输入错误请重新输入：");
an=0;
}
break;
case 6:
an = 1;
System.out.println("谢谢使用！");
break;
default:
System.out.println("输入错误:");
break;
}
} while (an == 0);
}
7.练习2
// 数据主体：一组订单信息
String[] names = new String[4]; // 订餐人名称
String[] dishMegs = new String[4]; // 所选菜品
int[] times = new int[4]; // 送餐时间
String[] addresses = new String[4]; // 送餐地址
int[] states = new int[4]; // 订单状态： 0：已预定 1：已完成
double[] sumPrices = new double[4]; // 总金额
//初始化2个订单信息
names[0] = "张晴";
dishMegs[0] = "红烧带鱼 2份";
times[0] = 12;
addresses[0] = "天成路207号";
sumPrices[0] = 76.0;
states[0] = 1;
names[1] = "张晴";
dishMegs[1] = "鱼香肉丝 2份";
times[1] = 18;
addresses[1] = "天成路207号";
sumPrices[1] = 20.0;
// 供选择的菜品信息
String[] dishNames = { "红烧带鱼", "鱼香肉丝", "时令鲜蔬" }; // 菜品名称
double[] prices = new double[] { 38.0, 20.0, 10.0 }; // 菜品单价
int[] praiseNums = new int[3];
Scanner input = new Scanner(System.in);
int num = -1; // 用户输入0返回主菜单，否则退出系统
boolean isExit = false; // 标志用户是否退出系统： true:退出系统
System.out.println("\n欢迎使用“吃货联盟订餐系统”");
// 循环：显示菜单，根据用户选择的数字执行相应功能
do {
// 显示菜单
System.out.println("****************************");
System.out.println("1、我要订餐");
System.out.println("2、查看餐袋");
System.out.println("3、签收订单");
System.out.println("4、删除订单");
System.out.println("5、我要点赞");
System.out.println("6、退出系统");
System.out.println("****************************");
System.out.print("请选择：");
int choose = input.nextInt(); // 记录用户选择的功能编号
boolean isAdd = false; //记录是否可以订餐
boolean isSignFind = false; //找到要签收的订单
boolean isDelFind = false; //找到要删除的订单
// 根据用户选择的功能编号执行相应功能
switch (choose) {
case 1:
// 我要订餐
System.out.println("***我要订餐***");
for (int j = 0; j < names.length; j++) {
if(names[j] == null){ //找到第一个空位置，可以添加订单信息
isAdd = true; //置标志位，可以订餐
System.out.print("请输入订餐人姓名：");
String name = input.next();
// 显示供选择的菜品信息
System.out.println("序号" + "\t" + "菜名"+"\t"+"单价");
for (int i = 0; i < dishNames.length; i++) {
String price = prices[i] + "元";
String priaiseNum = (praiseNums[i]) > 0 ? praiseNums[i]
+ "赞" : "";
System.out.println((i + 1) + "\t" + dishNames[i] + "\t" +price+"\t"+ priaiseNum);
}
// 用户点菜
System.out.print("请选择您要点的菜品编号:");
int chooseDish = input.nextInt();
System.out.print("请选择您需要的份数:");
int number = input.nextInt();
String dishMeg = dishNames[chooseDish - 1]
+" "+ number + "份";
double sumPrice = prices[chooseDish - 1] * number;
//餐费满50元，免送餐费10元
double deliCharge = (sumPrice>=50)?0:6;
System.out.print("请输入送餐时间（送餐时间是10点至20点间整点送餐）:");
int time = input.nextInt();
while (time < 10 || time > 20) {
System.out.print("您的输入有误，请输入10~20间的整数！");
time = input.nextInt();
}
System.out.print("请输入送餐地址：");
String address = input.next();
//无需添加状态，默认是0，即已预定状态。
System.out.println("订餐成功！");
System.out.println("您订的是："+dishMeg);
System.out.println("送餐时间："+time+"点");
System.out.println("餐费："+sumPrice+"元，送餐费"+deliCharge+"元，总计："+(sumPrice+deliCharge)+"元。");
//添加数据
names[j] = name;
dishMegs[j] = dishMeg;
times[j] = time;
addresses[j] = address;
sumPrices[j] = sumPrice+deliCharge;
break;
}
}
if(!isAdd){
System.out.println("对不起，您的餐袋已满！");
}
break;
case 2:
// 查看餐袋
System.out.println("***查看餐袋***");
System.out.println("序号\t订餐人\t餐品信息\t\t送餐日期\t送餐地址\t\t总金额\t订单状态");
for(int i=0;i<names.length;i++){
if(names[i]!=null){
String state = (states[i]==0)?"已预定":"已完成";
String date = times[i]+"日";
String sumPrice = sumPrices[i]+"元";
System.out.println((i+1)+"\t"+names[i]+"\t"+dishMegs[i]+"\t"+date+"\t"+addresses[i]+"\t"+sumPrice+"\t"+state);
}
}
break;
case 3:
// 签收定单
System.out.println("***签收定单***");
System.out.print("请选择要签收的订单序号：");
int signOrderId = input.nextInt();
for(int i=0;i<names.length;i++){
//状态为已预定，序号为用户输入的订单序号：可签收
//状态为已完成，序叼为用户输入胡订单序号：不可签收
if(names[i]!=null && states[i]==0 && signOrderId==i+1){
states[i] = 1; //将状态值置为已完成
System.out.println("订单签收成功！");
isSignFind = true;
}else if(names[i]!=null && states[i]==1 && signOrderId==i+1){
System.out.println("您选择的订单已完成签收，不能再次签收！");
isSignFind = true;
}
}
//未找到的订单序号：不可签收
if(!isSignFind){
System.out.println("您选择的订单不存在！");
}
break;
case 4:
// 删除订单
System.out.println("***删除订单***");
System.out.print("请输入要删除的订单序号:");
int delId = input.nextInt();
for(int i=0;i<names.length;i++){
//状态值为已完成 序号值为用户输入的序号：可删除
//状态值为已预定 序号值为用户输入的序号：不可删除
if(names[i]!=null && states[i]==1 && delId==i+1){
isDelFind = true;
//执行删除操作:删除位置后的元素依次前移
for(int j=delId-1;j<names.length-1;j++){
names[j] = names[j+1];
dishMegs[j] = dishMegs[j+1];
times[j] = times[j+1];
addresses[j] = addresses[j+1];
states[j] = states[j+1];
}
//最后一位清空
names[names.length-1] = null;
dishMegs[names.length-1] = null;
times[names.length-1] = 0;
addresses[names.length-1] = null;
states[names.length-1] = 0;
System.out.println("删除订单成功！");
break;
}else if(names[i]!=null && states[i]==0 && delId==i+1){
System.out.println("您选择的订单未签收，不能删除！");
isDelFind = true;
break;
}
}
//未找到该序号的订单：不能删除
if(!isDelFind){
System.out.println("您要删除的订单不存在！");
}
break;
case 5:
// 我要点赞
System.out.println("***我要点赞***");
// 显示菜品信息
System.out.println("序号" + "\t" + "菜名"+"\t"+"单价");
for (int i = 0; i < dishNames.length; i++) {
String price = prices[i] + "元";
String priaiseNum = (praiseNums[i]) > 0 ? praiseNums[i]
+ "赞" : "0赞";
System.out.println((i + 1) + "\t" + dishNames[i] + "\t" +price+"\t"+ priaiseNum);
}
System.out.print("请选择您要点赞的菜品序号：");
int priaiseNum = input.nextInt();
praiseNums[priaiseNum-1]++; //赞数加1
System.out.println("点赞成功！");
break;
case 6:
// 退出系统
isExit = true;
break;
default:
//退出系统
isExit = true;
break;
}
if (!isExit) {
System.out.print("输入0返回：");
num = input.nextInt();
} else {
break;
}
} while (num == 0);
System.out.println("谢谢使用，欢迎下次光临！");
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