如何检查 Java 字符串是否至少包含一个大写字母、小写字母和数字？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/40336374/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How do I check if a Java String contains at least one capital letter, lowercase letter, and number?
提问by Michael Drum
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.
我知道我可以使用一系列遍历字符串的 for 循环来做到这一点，但这将是糟糕的编程。好吧，我的教授更喜欢我不要这样做。我想使用正则表达式来做到这一点。
采纳答案by CyprUS
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 :
对于简单的字符串检查，单次扫描字符串就足够了。由于正则表达式不会提供任何显着的好处，这里是一个简单的 for 循环来实现相同的：
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;
}
Test run:
测试运行：
System.out.println(checkString("aBCd1")); // output is true
System.out.println(checkString("abcd")); //output is false
I think this should help OP's particular problem.
我认为这应该有助于解决 OP 的特殊问题。
回答by Ghost Developer
Try regular expression
试试正则表达式
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).+$
descriptions are as follow
(?=.*[a-z]) -- check lower case letter
(?=.*[A-Z]) -- check upper case letter
(?=.*\d) -- check one digit exists
回答by Saad
You can use Character class of java. So for lowercase, Character.isLowerCase(ch)Character.isUpperCase(ch). For this you have to iterate over the string. I know that bit is irrelevant to you, however you can use "\\d+"for numbers in a string.
您可以使用java的Character类。所以对于小写，Character.isLowerCase(ch)Character.isUpperCase(ch). 为此，您必须遍历 string。我知道该位与您无关，但是您可以将其"\\d+"用于字符串中的数字。
回答by sopheamak
you can use :
您可以使用 ：
public static boolean isTextContainUpperCase(String text) {
if (StringUtils.isEmpty(text)) {
return false;
}
return !text.equals(text.toLowerCase());
}
回答by Yhondri
Example of @goshDeveloper's answer.
@goshDeveloper 的回答示例。
First create a Pattern variable with regular expression you want.
首先用你想要的正则表达式创建一个 Pattern 变量。
public final Pattern textPattern = Pattern.compile("^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).+$");
Second you can use it like this:
其次，您可以像这样使用它：
public boolean isTextValid(String textToCheck) {
return textPattern.matcher(textToCheck).matches();
}
回答by ?ukasz K
Using Java 9:
使用 Java 9：
public boolean isValid(String value) {
return containsLowerCase(value) &&
containsUpperCase(value) &&
containsNumber(value);
}
private boolean containsLowerCase(String value) {
return contains(value, i -> Character.isLetter(i) && Character.isLowerCase(i));
}
private boolean containsUpperCase(String value) {
return contains(value, i -> Character.isLetter(i) && Character.isUpperCase(i));
}
private boolean containsNumber(String value) {
return contains(value, Character::isDigit);
}
private boolean contains(String value, IntPredicate predicate) {
return value.chars().anyMatch(predicate);
}
回答by Tanumay Saha
If you are looking to check whether your string contains uppercase letter or not, you can use below pattern:
如果您想检查您的字符串是否包含大写字母，您可以使用以下模式：
String s="abcDe_shdgwU"; //you can have any String here
if(s.matches(".*[A-Z].*"))
System.out.println("The String contains Uppercase letter(s)");
else
System.out.println("does not contain Uppercase letter(s)");
Hope that helps. Thank you. Regards, Tanumay Saha
希望有帮助。谢谢你。问候， 塔努迈萨哈
