java - 具有数组列表的彩票类，没有重复的数字并且不能超出范围

Question

我正在上 Java 入门课。我对这种编程语言比较陌生。我必须制作一个彩票类，其中用户必须输入 1-9 之间的数字，并且不能重复。为此，我制作了一个数组列表。这是我到目前为止所拥有的:

public class Lottery {

private int lotteryNumber[] = new int[5];
private ArrayList<Integer> userLotteryPicks = new ArrayList<Integer>(5);

public Lottery() {

    Random myRan = new Random();

    for (int i = 0; i < lotteryNumber.length; i++) {
        lotteryNumber[i] = myRan.nextInt(9) + 1;
        for (int j = 0; j < i; j++) {
            if ((lotteryNumber[i] == (lotteryNumber[j])) && (i != j)) {
                i = 0;
            }
        }
    }
}

public void getUserPicks() {

    Scanner keyboard = new Scanner(System.in);

    int userPicks = 0;

    for (int i = 0; i < 5; i++) {
        System.out.println("Enter your 5 lucky numbers for the lottery: ");
        userPicks = keyboard.nextInt();

        if (userPicks < 10 && userPicks > 0) {
            userLotteryPicks.add(userPicks);
        } else {
            System.out.println("Not a valid entry. "
                    + "Make sure the number is between 1-9 "
                    + "Enter your 5 numbers again \n");
            i = 0;
        }
        for (int j = 0; j < i; j++) {
            if ((userLotteryPicks.get(i) == (userLotteryPicks.get(j))) && (i != j)) {
                i = 0;
                System.out.println("You put an invalid entry. No duplicates allowed"
                        + " please start over. \n ");
            }
        }
    }
}

getUserPicks 是我遇到问题的方法。如果用户第一次输入重复项，则下一个循环会说他们输入的任何内容都是重复项。感谢您的任何帮助。

Answer 1

使用HashSet代替ArrayList来存储数字。集合不允许重复。对于任何错误的输入，您无需重新开始。检查下面的代码。

// Change this initialization to Set instead of ArrayList
private Set<Integer> userLotteryPicks = new HashSet<Integer>(5);

public void getUserPicks() {
  Scanner keyboard = new Scanner(System.in);
  int userPicks = 0;
  System.out.println("Enter your 5 lucky numbers for the lottery: ");
  for (int i = 0; i < 5; i++) {
    userPicks = keyboard.nextInt();

    boolean unique = false;
    if (userPicks < 10 && userPicks > 0) {
      unique = userLotteryPicks.add(userPicks);   //if duplicate, then it return false.
    } else {
      System.out.println("Not a valid entry. "
          + "Make sure the number is between 1-9.");
      i--;  // for wrong inputs, decrease the counter by again, instead of start over again.
      continue;
    }
    if (!unique) {
      System.out.println("You put an invalid entry. No duplicates allowed. Enter the number again.");
      i--;  // for wrong inputs, decrease the counter by again, instead of start over again.
    }
  }
}