Allow only alphanumeric characters using a-zA-Z0-9 Java regular expression

How to allow only alphanumeric characters in string using a-zA-Z0-9 pattern?

Regular expression can be used to check if the string contains only alphanumeric characters or not.

Let’s see the pattern in action.


Note: The pattern given in the example (a-zA-Z0-9) only works with ASCII characters. It fails to match the Unicode characters.

If the application needs Unicode characters compatible pattern matching, then following pattern should be used.

How to remove special characters from String using regular expressions in Java?

The similar pattern can be used to remove unwanted characters from string as well. For example, if you want to remove everything but the alphabets and numbers from the String, you can use the same pattern but with replaceAll() method of string instead of matches() method.

We are going to use following pattern to remove all special characters from the String.

It means match any character which is not between a to z, A to Z and 0 to 9.


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