I've used regex (using jakarta-regexp-1.2.jar) to validate email address . The 
code is as follows :
String email = "abc@abc.com"
String regExp = "^\\w+([_]*[\\-\\.]?[_]*\\w+[_]*)*@\\w+([_]*[\\-\\.]?[_]*\\w+[_]
*)*(\\.\\w{1}\\w+)+$";
          try {
  	      RE reg = new RE(regExp);
              if(!(reg.match(eMail))) {
  		return false;
              }
          } catch(Exception e) {
              return false;
          }
          return true; 


Now if I pass email address as a big one e.g. 
abcyz1234567890abcyz1234567890abcyz1234567890@abwxycom  which is a wrong one, 
the system hangs .