如何检查Java String是否包含至少一个大写字母，小写字母和数字？

问题描述

我知道我可以通过一系列for循环遍历字符串的for循环来做到这一点，但那将是糟糕的编程。好吧，我的教授更喜欢我不这样做。我想使用正则表达式来执行此操作。

I know that I could do this with a series of for loops that iterate through the string but that would be terrible programming. Well, my professor prefers I don't do it this way. I'd like to use regular expressions to do this.

推荐答案

对于简单的字符串检查，单个扫描字符串是足够。由于Regex不会提供任何显着的好处，这里有一个简单的for循环来实现相同的目的：

For a simple string check, a single sweep through the string is enough. Since Regex will not offer any significant benefit, here is a simple for loop to achieve the same :

private static boolean checkString(String str) {
    char ch;
    boolean capitalFlag = false;
    boolean lowerCaseFlag = false;
    boolean numberFlag = false;
    for(int i=0;i < str.length();i++) {
        ch = str.charAt(i);
        if( Character.isDigit(ch)) {
            numberFlag = true;
        }
        else if (Character.isUpperCase(ch)) {
            capitalFlag = true;
        } else if (Character.isLowerCase(ch)) {
            lowerCaseFlag = true;
        }
        if(numberFlag && capitalFlag && lowerCaseFlag)
            return true;
    }
    return false;
}

试运行

System.out.println(checkString("aBCd1")); // output is true
System.out.println(checkString("abcd")); //output is false

我认为这应该有助于OP的特殊问题。

I think this should help OP's particular problem.

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