Java regex pattern credit card validation

/**
 * @author lautturi.com 
 * Java example: validate the bank card number using regex in java
 */


import java.util.*;
import java.util.regex.*;

public class Lautturi {

	public static void main(String[] args) {
		String creditCardNumber = "4512332233333255";
		String visaRegex = "^4[0-9]{15}";
		String americanExpressRegex = "3[4-7][0-9]{13}";
		String masterCardRegex = "5[1-5][0-9]{14}|2(22[1-9][0-9]{12}|720[0-9]{12})";
		
		Pattern p = Pattern.compile(visaRegex);
		Matcher m = p.matcher(creditCardNumber);
		Boolean b = m.matches();     
		if(b) {
			System.out.println("It's a valid card number");
		}
	}
}