Java实现简单登陆，注册，退出

    public static void login(int[] message){
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入账号：");
        int id = scanner.nextInt();
        int i = 0;
        for(;i<message.length;i++){
            if(message[i] == id){
                System.out.println("登陆成功");
                break;
            }
        }
        if(i == message.length) {
            System.out.println("登陆失败");
        }
    }
    public static void register(int[] message){
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入账号：");
        int id = scanner.nextInt();
        //是否之前存在id,存在，注册失败
        for(int i=0;i<message.length;i++){
            if(message[i] == id){
                System.out.println("注册失败");
                return;
            }
        }
        for(int i=0;i<message.length;i++){
            if(message[i] == 0){
                message[i] = id;//找到合适位置放id
                System.out.println("注册成功");
                break;
            }
        }
    }
    public static void main(String[] args) {
        int[] message = new int[10];
        while (true) {
            System.out.println("1.登陆 2注册  3退出");
            Scanner scanner = new Scanner(System.in);
            int choice = scanner.nextInt();
            if (choice == 3) {
                return;
            }
            switch (choice) {
                case 1:
                    login(message);
                    break;
                case 2:
                    register(message);
                    break;
                default:
                    System.out.println("输入错误");
            }
        }
    }