This Java example demonstrates how to write a regular expression 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.
Java Alphanumeric Regex Example
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class TestDemo {
public static void main(String[] args) {
List < String > names = new ArrayList < String > ();
names.add("SourceCodeExample");
names.add("SourceCodeExample123");
names.add("SourceCodeExample-----////"); //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());
}
}
}
Output:
true
true
false
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