在java中你怎么看一个数字是否只包含1,2,3？

Question

我有一个java问题，我必须看看9位数字是否只包含1,2,3 - 并且还有1和2的相同数字3，反之亦然。

例如：

• 123231312 = true
• 111111111 = false
• 112731923 = false

Answer 1

 private boolean onlyContainsOneTwoAndThree(int number) {
    char[] digitsFromNumber = String.valueOf(number).toCharArray(); // convert to char[] for easier manipulation.
    int oneCounter = 0;
    int twoCounter = 0;
    int threeCounter = 0;

    for (char digit : digitsFromNumber) {
        switch (digit) {
            case '1':
                oneCounter++;
                break;
            case '2':
                twoCounter++;
                break;
            case '3':
                threeCounter++;
                break;
            default:
                return false;
        }
    }
    if ((oneCounter == twoCounter) && (twoCounter == threeCounter)) {
        return true; // return true only when 1,2 and 3 appear exactly the same number of times.
    }
    return false;
}

Answer 2

boolean correct(String input) {
    Map<Character, Integer> map = new HashMap<>();
    char[] charArray = input.toCharArray();

    for (char num : charArray) {
        Integer count = map.get(num);
        if (count == null) {
            count = 0;
        }
        map.put(num, count.intValue() + 1);
    }

    Integer val = map.get('1');
    if (val != null && val == map.get('2') && val == map.get('3') &&
        map.size() == 3) {
        return true;
    }

    return false;
}

Answer 3

public static boolean isGood(String input) {
     return input.length() == 9 && 2D == input.chars()
                                            .parallel()
                                            .mapToObj(i -> (char)i)
                                            .map(Character::getNumericValue)
                                            .map(number -> number >= 1 && number <= 3 ? number : Integer.MAX_VALUE)
                                            .mapToInt(number -> number).average().orElse(-1);
}

Answer 4

String s = Integer.toString(number);
System.out.println(s.contains("1") && s.contains("2") && s.contains("3"));