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Program: How to validate user name using regular expression?


Description:

The below given example shows how to validate a user name. The regular expression pattern allows lower case alphanumeric characters, allows '-', '_'. Incase if you want to support uppercase characters then regular expression should be ^[a-zA-Z0-9_-]{6,14}$


Code:
package com.java2novice.regex;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class MyUsernameValidate {

	private static Pattern usrNamePtrn = Pattern.compile("^[a-z0-9_-]{6,14}$");
	
	public static boolean validateUserName(String userName){
		
		Matcher mtch = usrNamePtrn.matcher(userName);
		if(mtch.matches()){
			return true;
		}
		return false;
	}
	
	public static void main(String a[]){
		System.out.println("Is 'java2novice' a valid user name? "
						+validateUserName("java2novice"));
		System.out.println("Is 'cric' a valid user name? "
						+validateUserName("cric"));
		System.out.println("Is 'JAVA2NOVICE' a valid user name? "
						+validateUserName("JAVA2NOVICE"));
		System.out.println("Is 'java.2.novice' a valid user name? "
						+validateUserName("java.2.novice"));
		System.out.println("Is 'java_2-novice' a valid user name? "
						+validateUserName("java_2-novice"));
	}
}

Output:
Is 'java2novice' a valid user name? true
Is 'cric' a valid user name? false
Is 'JAVA2NOVICE' a valid user name? false
Is 'java.2.novice' a valid user name? false
Is 'java_2-novice' a valid user name? true
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List Of Regular Expression Sample Programs:

  1. Simple regex pattern matching using string matches().
  2. Simple java regex using Pattern and Matcher classes.
  3. Java regex with case insensitive.
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  7. How to validate user name using regular expression?
  8. How to validate email address using regular expression?
  9. How to validate password using regular expression?
  10. How to validate file extensions using regular expression in java?
  11. How to validate date format using regular expression in java?
  12. How to capture or extract a value(s) from text using regular expression in java?
  13. How to split a string using regular expression?
Knowledge Centre
String Vs StringBuffer
We know that String is immutable object. We can not change the value of a String object once it is initiated. If we try to change the value of the existing String object then it creates new object rather than changing the value of the existing object. So incase, we are going to do more modificatios on String, then use StringBuffer. StringBuffer updates the existing objects value, rather creating new object.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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