java - 使用数组还是字符效率更高？

Question

这是确定字符串中至少有两个唯一字符的最有效方法吗？我应该使用数组来保存字符吗？谢谢

public static Boolean checkPW(String pw) {
    Boolean validLower = false, validUpper = false, validNumber = false;
    char lowerCompare = '0', upperCompare = '0', numberCompare = 'a';

    for(int position = 0; position < pw.length(); ++position) {
        char character = pw.charAt(position);
        if(character >= 'a' && character <= 'z') {
            if(lowerCompare == '0')
                lowerCompare = character;
            else if(lowerCompare != character)
                validLower = true;
        } // lower-case if END
    } // for-loop END
if(validLower)
    return true;
else
    return false;
} // checkPW END

Answer 1

如果我必须在 Java 中执行此操作，在生产中，我可能会在此处使用一个集合:

String input = "abcdefgzz";
char[] letters = input.toCharArray();
Set<Character> set = new HashSet<>();
boolean valid = false;
for (char letter : letters) {
    set.add(letter);
    if (set.size() > 1) {
        valid = true;
        break;
    }
}

if (valid) {
    System.out.println("Minimum of two unique letters");
}
else {
    System.out.println("Only one unique letter");
}