//声明数组
int[] array;
//分配内存空间
array = new int[6];
//给数组赋值
array[0] = 1;
array[1] = 2;
array[2] = 3;
array[3] = 4;
array[4] = 5;
array[5] = 6;
int[] array2 = {1,2,3,4,5,6};
int[] array3 = new int[]{1,2,3,4,5,6};
综合例子
import java.util.Arrays;
import java.util.Scanner;
public class Test {
//初始化数据
static String[] names = {"张三","李四","王五","小明"};
static int[] ages = {22,23,20,20};
static String[] states = {"正常","正常","正常","正常"};
public static void main(String[] args) {
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.print("请选择：");
num = scanner.nextInt();
switch(num) {
case 1:
System.out.println("------查询用户------");
System.out.println("编号\t\t姓名\t\t年龄\t\t状态");
for(int i=0;i<names.length;i++) {
if(names[i]!=null) {
System.out.println((i+1)+"\t\t"+names[i]+"\t\t"+ages[i]+"\t\t"+states[i]);
}
}
System.out.print("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 2:
System.out.println("------添加用户------");
System.out.print("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.print("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.print("请输入"+name+"的年龄：");
int age = scanner.nextInt();
ages[index] = age;
states[index] = "正常";
}
}
System.out.print("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 3:
System.out.println("------删除用户------");
if(names[0]==null) {
System.out.println("用户已全部删除！");
}else {
System.out.print("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];
}
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.print("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 4:
System.out.println("------账号冻结------");
System.out.print("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.print("输入0返回上级菜单");
num = scanner.nextInt();
break;
case 5:
System.out.println("------账号解封------");
System.out.print("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+"已解封，请勿重复操作！");
}else {
states[index] = "正常";
System.out.println(name+"成功解封！");
}
}else {
System.out.println(name+"不存在，请重新输入！");
}
System.out.print("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;
}
}while(num==0);
}
/**
* 判断用户输入的姓名是否已经存在于数组中
*/
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;
}
}
