A list of useful regexp

30 Oct 2011 at 00:00:00 - 0 comment(s)

regexp or in other words regular expression is something you have to regularly use in your applications. I've decided to write this post as a placeholder for regexp I believe are common and useful such as regexp for email validation or some you might use to replace characters in a string. I might write some piece of java code but you can use these regular expression in many other languages.

1. regexp for validating email address


But here is actually what I use to validate email address:

  public boolean isValidEmail(String input) {
    Pattern p = Pattern.compile("^\\.|^\\@");
    Matcher m = p.matcher(input);
    if (m.find())
      return false;
    p = Pattern.compile("^www\\.");
    m = p.matcher(input);
    if (m.find())
      return false;
    p = Pattern.compile("[^A-Za-z0-9\\.\\@_\\-~#]+");
    m = p.matcher(input);
    StringBuffer sb = new StringBuffer();
    boolean result = m.find();
    boolean deletedIllegalChars = false;
    while(result) {
      deletedIllegalChars = true;
      m.appendReplacement(sb, "");
      result = m.find();
    // Add the last segment of input to the new String
    input = sb.toString();
      return false;
    return true;

2. regexp to validate username of type test@test


3. regexp to replace multiple spaces


4. regexp to replace any characters that is not alphanumeric



Don't hesitate to propose some more in the comments.


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