Regular expression using Java

Regular expression (regex or regexp) is used for searching using String pattern matching. Regex is a sequence of characters that forms a search pattern .

JDK comes up with built-in api for regex manipulation.Regex can be implemented using the “Pattern” and the “Matcher” class.

Sample program: 

       public static void main(String args[]) {

             

               boolean gotit = false;

               // -------------------------------------

             String line = "Rubesh is a technology (XYZ technology solutions) !. mail - samson@gmail.com mobile - 754-543-5843";

             String pattern = "[^a-z]";

            

             // Create a Pattern object

             Pattern r = Pattern.compile(pattern);

             // Now create matcher object.

             Matcher matcher = r.matcher(line);

             while (matcher.find()) {

                  System.out.print(matcher.group());

              gotit = true;

          }

          if(!gotit){

              System.out.println("No results !!!");

          }

       }

If you want to get the start & end index of a selected letter in the output you can use the matcher.start() and matcher.end().

Input / output samples:

Regex pattern                Output

[a-z]                              ubeshisatechnologytechnologysolutionsmailsamsongmailcommobile

[A-Z]                            RXYZ

[A-Za-z]                       RubeshisatechnologyXYZtechnologysolutionsmailsamsongmailcommobile

[a-z0-9_-]                    ubeshisatechnologytechnologysolutionsmail-samsongmailcommobile-754-543-5843

[a-z0-9_-]{4,10}         ubeshtechnologytechnologysolutionsmailsamsongmailmobile754-543-58

You can try out regex directly using www.regexpal.com