问题
I need to analyze a string in JAVA to find out if it has both letters and numbers. So this is what I have so far. The variable pass is a String of maximum 8 characters/numbers that is inputted by the user.
if(pass.matches("[^A-Za-z0-9]"))
{
System.out.println("Valid");
}
else
{
System.out.println("Invalid");
}
回答1:
Your question is a little ambiguous.
If you just want to know whether the string contains letters or numbers (but perhaps only letters or only numbers) and nothing else, then the regex :
pass.matches("^[a-zA-Z0-9]+$");
will return true.
If you want to check whether it contains both letters and numbers, and nothing else, then it is more complex, but something like:
pass.matches("^[a-zA-Z0-9]*(([a-zA-Z][0-9])|([0-9][a-zA-Z]))[a-zA-Z0-9]*$");
all the best
回答2:
I'd use StringUtils.isAlphanumeric. Your code will look like this:
if (StringUtils.isAlphanumeric(pass)) {
//valid
} ...
You say you also want a maximum of 8 characters. You can do it like this:
if (StringUtils.isAlphanumeric(pass) && StringUtils.length(pass) <= 8) {
//valid
} ...
The advantage of using StringUtils again for the length is that you won't get a NullPointerException if pass is null. Alternatively, you could just use pass.length(), but you risk getting a NullPointerException.
来源：https://stackoverflow.com/questions/16430684/how-to-analyze-a-string-in-java-to-make-sure-that-it-has-both-letters-and-number