Mainly for Java basic knowledge: review applications including variables, data types, process control, loops, arrays, etc.
1. Console-based user management system
- Query users: output all user information saved in the system on the console.
- Add user: add new user information to the system, if the added user already exists, a prompt message will be given.
- Delete user: Enter the user name to delete. If the entered user name does not exist, a prompt message will be given.
- Account freeze: Enter a user name to perform a freeze operation. If the entered user name does not exist or the user has been frozen, a corresponding prompt will be given.
- Account unfreezing: Enter the user name to unblock the account. If the entered user name does not exist or the user status is normal, a corresponding prompt will be given.
- Exit the system: Jump out of the loop and give a prompt message.
Use an array to represent the user's name, age, and status. The
reference code is as follows:
import java.util.Arrays;
import java.util.Scanner;
public class demo_001 {
/*初始化用户数据（用户名，年龄，状态）
* 定义在main方法外来扩大数组作用域
要改成静态的，main方法是静态的，外面定义的相当于成员变量，
要不然无法访问*/
static String[] names = {
"张三","李四","王五","小明"};
static int[] ages = {
22,23,20,22};
static String[] states = {
"正常","正常","正常","正常"};
public static void main(String[] args) {
/*这里有一个细节注意的是scanner对象创建不能放在循坏里，
如果放在循环里意味着每循环一次就会创建一个，这样会造成空间的浪费，
我们只需要一个scanner对象就可以了，所以放在循环体外面就行*/
Scanner scanner = new Scanner(System.in);
int num;
do {
System.out.println("------欢迎使用用户管理系统------");
System.out.println("1.查询用户");
System.out.println("2.添加用户");
System.out.println("3.删除用户");
System.out.println("4.账号冻结");
System.out.println("5.账号解冻");
System.out.println("6.退出系统");
System.out.println("请选择：");
num = scanner.nextInt();
switch(num) {
case 1:
//System.out.println("执行查询用户操作");
System.out.println("-------查询用户------");
System.out.println("编号\t\t姓名\t\t年龄\t\t状态");
//遍历三个数组，长度都一样
for(int i=0;i<names.length;i++) {
if(names[i] !=null) {
// \t是一个制表符，等于一个table
System.out.println((i+1)+"\t\t"+names[i]+"\t\t"+ages[i]+"\t\t"+states[i]);
}
}
System.out.println("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 2:
//System.out.println("执行添加用户操作");
System.out.println("-------添加用户------");
//实现动态扩充
System.out.println("请输入用户姓名：");
String name = scanner.next();
if(nameIsExist(name)) {
System.out.println(name+"已存在,请勿重复添加！");
}else {
if(names[names.length-1]!=null) {
//创建新的数组，并且将老数组的值存入新数组
names = Arrays.copyOf(names, names.length+1);
names[names.length-1] = name;
System.out.println("请输入"+name+"的年龄");
int age = scanner.nextInt();
ages = Arrays.copyOf(ages, ages.length+1);
ages[ages.length-1] = age;
states = Arrays.copyOf(states, states.length+1);
states[states.length-1] = "正常";
}
else {
int index = getFirstNull();
names[index] = name;
System.out.println("请输入"+name+"的年龄");
int age = scanner.nextInt();
ages[index] = age;
states[index] = "正常";
}
}
// if(names[names.length-1]!=null) {
// System.out.println("数组已经填满，新用户无法加入");
// }else {
// System.out.println("请输入用户姓名");
// String name = scanner.next();
// boolean flag = nameIsExist(name);
// if(flag) {
// System.out.println(name+"已存在，请勿重复添加");
// }else {
// names[names.length-1] = name;
// System.out.println("请输入"+name+"的年龄");
// int age = scanner.nextInt();
// ages[ages.length-1] = age;
// states[states.length-1]= "正常";
// System.out.println(name+"添加成功");
// }
// }
System.out.println("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 3:
//System.out.println("执行删除用户操作");
System.out.println("-------删除用户------");
if(names[0] == null) {
System.out.println("用户已经全部删除！");
}else {
System.out.println("请输入用户名");
name = scanner.next();
if(nameIsExist(name)) {
int index = getIndex(name);
if(index>=0) {
for(int i=index;i<names.length-1;i++) {
names[i] = names[i+1];
ages[i] = ages[i+1];
states[i] = states[i+1];
}
//把数组最后一位置为空
names[names.length-1] = null;
ages[ages.length-1] = 0;
states[states.length-1] = null;
}
}else {
System.out.println("您输入的用户不存在！");
}
}
System.out.println("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 4:
//System.out.println("执行账号冻结操作");
System.out.println("-------账号冻结------");
System.out.println("请输入用户名：");
name = scanner.next();
if(nameIsExist(name)) {
int index = getIndex(name);
String state = states[index];
if(state.equals("冻结")) {
System.out.println(name+"账号已经被冻结，请勿重复操作！");
}else {
states[index] = "冻结";
System.out.println(name+"冻结成功");
}
}else {
System.out.println("您输入的用户不存在！");
}
System.out.println("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 5:
//System.out.println("执行账号解冻操作");
System.out.println("-------账号解冻------");
System.out.println("请输入用户名：");
name = scanner.next();
if(nameIsExist(name)) {
int index = getIndex(name);
String state = states[index];
if(state.equals("正常")) {
System.out.println(name+"已解冻，请勿重复操作！");
}else {
states[index] = "正常";
System.out.println(name+"成功解冻");
}
}else {
System.out.println(name+"不存在，请重新输入！");
}
System.out.println("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 6:
System.out.println("感谢使用本系统，再见！");
break;
default:
break;
}
}while(num<6);//while(num==0);也可以
}
/**
* 判断用户输入的姓名是否已经存在与数组中
*/
public static boolean nameIsExist(String name) {
for(int i=0;i<names.length;i++) {
if(name.equals(names[i])) {
return true;
}
}
return false;
}
/**
* 找到名字在数组中的下标
*/
public static int getIndex(String name) {
for(int i=0;i<names.length;i++) {
if(name.equals(names[i])) {
return i;
}
}
return -1;
}
/**
* 找到数组中第一个为空的下标
*/
public static int getFirstNull() {
for(int i=0;i<names.length;i++) {
if(names[i] == null) {
return i;
}
}
return -1;
}
}