Regular expression in java

http://java.sun.com/developer/technicalArticles/releases/1.4regex/

String input = "something";

1. write a regular expression

String regex="your_reg_ex"; 

2. create a pattern object compiling your regex

Pattern p = Pattern.compile(regex);

3. create a matcher object that will match input string with the compiled regex

Matcher m = p.matcher(input);

4. check whether any matching found

if (m.find())
{
//5. if found, the matched portion will be available at m.group()
String found = m.group();
// do whatever u like
 }

let, input = "fjkl;pokjhA123ss456Apghkit"
u want to read block between 2 A's
regex = (?<=X).*?(?=X) where X = "A" here output = "123ss456" u can only use fixed length string in (?<=X), never use .*? or + in X otherwise u'll get exception

Look-behind group does not have an obvious maximum length near index ..

Java code for this:

 
   String regularExp = "(?<=A).*?(?=A)";

 
   String input = "fjkl;pokjhA123ss456Apghkit";
 

   Pattern pattern = Pattern.compile(regularExp);

   
   Matcher matcher =  pattern.matcher(input);

      
      if(matcher.find())
         {

         String parsedData = matcher.group();
                 System.out.println(" Output ->"+parsedData);

          }