We can use the given regular expression used to validate user input in such a way that it allows only alphanumeric characters. Alphanumeric characters are all alphabets and numbers i.e. letters A–Z, a–z, and digits 0–9.
1. Alphanumeric regex pattern
With alphanumeric regex at our disposal, the solution is dead simple. A character class can set up the allowed range of characters. With an added quantifier that repeats the character class one or more times, and anchors that bind the match to the start and end of the string, we’re good to go.
Regex: ^[a-zA-Z0-9]+$
2. Alphanumeric regex example
List<String> names = new ArrayList<String>(); names.add("Lokesh"); names.add("LOkesh123"); names.add("LOkesh123-"); //Incorrect String regex = "^[a-zA-Z0-9]+$"; Pattern pattern = Pattern.compile(regex); for (String name : names) { Matcher matcher = pattern.matcher(name); System.out.println(matcher.matches()); }
Program Output.
true true false
It’s very easy when you know the basics. Right?
Happy Learning !!