A mini-post to expose a simple method to check the Regex expression:

public static void testExecuteRegex(String regexExpression, String valueToValidate) throws IOException {
	// Regex
	Pattern regexPattern = Pattern.compile(regexExpression);
	boolean valid=false;
	if(valueToValidate!=null) {
	        Matcher matcher = regexPattern.matcher(valueToValidate);
	        valid=matcher.matches();
	}else{ // The case of empty Regex expression must be accepted
	        Matcher matcher = regexPattern.matcher("");
	        valid=matcher.matches();
        }
        System.out.println("testExecuteRegex("+valueToValidate+")="+valid);
}

Examples:

// Regex for email format
String regexEmail = "([A-Za-z0-9\\.\\_\\-]+[\\.\\_\\-]*[A-Za-z0-9\\.\\_\\-]*)+@([A-Za-z0-9\\.\\_\\-]+[\\.]*[A-Za-z0-9\\.\\_\\-]+)+\\.[A-Za-z]+"; 

testExecuteRegex(regexEmail, "email@email.com");
testExecuteRegex(regexEmail, "em-ail@email.com");
testExecuteRegex(regexEmail, "em.ail@email.com");
testExecuteRegex(regexEmail, "em_ail@email.com");
testExecuteRegex(regexEmail, "d@email.com");
testExecuteRegex(regexEmail, "_em_ail@email.com");
testExecuteRegex(regexEmail, "_em_ailemail.com");
testExecuteRegex(regexEmail, "_em_ail@;email.com");
testExecuteRegex(regexEmail, "mff13@21f; fff@DD");

The result in the console could be:

testExecuteRegex(email@email.com)=true
testExecuteRegex(em-ail@email.com)=true
testExecuteRegex(em.ail@email.com)=true
testExecuteRegex(em_ail@email.com)=true
testExecuteRegex(d@email.com)=true
testExecuteRegex(_em_ail@email.com)=true
testExecuteRegex(_em_ailemail.com)=false
testExecuteRegex(_em_ail@;email.com)=false
testExecuteRegex(mff13@21f; fff@DD)=false

That’s all!!!

Huseyin OZVEREN