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java regex pattern validate hex code


Regular expressions

Regular expressions represents a sequence of symbols and characters expressing a string or pattern to be searched for within a longer piece of text. The abbreviation for regular expression is regex. In programming regular expressions are mainly used to define constraint on strings like password, email validation.

Regular expression hex code pattern

#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

This regular expression refers to a pattern which must start with a “#” symbol, follow by a letter from “a” to “f”, “A” to “Z” or a digit from “0” to 9″ with exactly 6 or 3 length.

Example

package com.codesjava;
 
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class RegexTest {
	private static final String PATTERN = 
			"((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,15})";
	public static void main(String args[]){ 
		List<String> values = new ArrayList<String>();	
		values.add("jaisingh1A@"); 
		values.add("Sjai12$"); 
		values.add("jaiA@");
		values.add("jai*");
 
		Pattern pattern = Pattern.compile(PATTERN);
		for (String value : values){
		  Matcher matcher = pattern.matcher(value);
		  if(matcher.matches()){
			  System.out.println("Password "+ value +" is valid");
		  }else{
			  System.out.println("Password "+ value +" is invalid");
		  }		  
		}
	}
}

Output

Password jaisingh1A@ is valid
Password Sjai12$ is valid
Password jaiA@ is invalid
Password jai* is invalid
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