public static boolean isMailValid(final String emailAddress){
  final String QUOTEDSTRING="\"(?:[^\"\\\\]|\\\\\\p{ASCII})*\"";
  final String ATOM="[^()<>@,;:\\\\\".\\[\\] \\x28\\p{Cntrl}]+";
  final String WORD="(?:" + ATOM + "|"+ QUOTEDSTRING+ ")";
  final String SUBDOMAIN="(?:" + ATOM + "|\\[(?:[^\\[\\]\\\\]|\\\\\\p{ASCII})*\\])";
  final String DOMAIN=SUBDOMAIN + "(?:\\." + SUBDOMAIN+ ")*";
  final String LOCALPART=WORD + "(?:\\." + WORD+ ")*";
  final String EMAIL=LOCALPART + "@" + DOMAIN;
  final String regex="(\\s*" + EMAIL + "\\s*)*";
  return emailAddress.matches(regex);
}

public static boolean isMailValid ( final String emailAddress ) { final String QUOTEDSTRING = "\"(?:[^\"\\\\]|\\\\\\p{ASCII})*\"" ; final String ATOM = "[^()<>@,;:\\\\\".\\[\\] \\x28\\p{Cntrl}]+" ; final String WORD = "(?:" + ATOM + "|" + QUOTEDSTRING + ")" ; final String SUBDOMAIN = "(?:" + ATOM + "|\\[(?:[^\\[\\]\\\\]|\\\\\\p{ASCII})*\\])" ; final String DOMAIN = SUBDOMAIN + "(?:\\." + SUBDOMAIN + ")*" ; final String LOCALPART = WORD + "(?:\\." + WORD + ")*" ; final String EMAIL = LOCALPART + "@" + DOMAIN ; final String regex = "(\\s*" + EMAIL + "\\s*)*" ; return emailAddress . matches ( regex ) ; }
allow multiple fully qualified email adresses seperated by spaces , or a blank string
