Solved

Regular Expression on string with braces in Java

Posted on 2009-05-12
3
1,141 Views
Last Modified: 2013-12-17
Hi guys,

I hope you could help me with these.  I need a regular expression that could split up the string below

{adfsadfd}{sdads}{asdf{asdf}{asdf}}{asdfsdf{dads}}

into

{adfsadfd}
{sdads}
{asdf{asdf}{asdf}}
{asdfsdf{dads}}



Currently I have "\\{([.*]*)[^}]*}"   but it doesn't work. It will also include the groups inside, which i don't want


Thanks in advance
0
Comment
Question by:xanbi
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 500 total points
ID: 24371754
([{](?:[^{]|[{][^{}]*})*})
0
 
LVL 40

Expert Comment

by:mrjoltcola
ID: 24375825
I would suggest that for recursive grammars, regular expressions are not usually adequate. You can usually write a "good enough" solution, but it will not be bulletproof for the whole grammar. There is a limit to how you can employ lookahead and lookbehind in a non-recursive approach, which regular expressions are.

Recursive descent parsers can be written for special cases, and I have provided a sample that will not descend into the nested {} as you asked. In a real parser we would usually return tree nodes and parse until there is no nesting left, but since you want the nesting to be preserved past 1 level, here is a sample that works, maybe you can use it.

// Simple recursive descent parser for matching nested tokens
public class Main {
	  public static void main(String [] args) {
	       String s = "{adfsadfd}{sdads}{asdf{asdf}{asdf}}{asdfsdf{dads}}";
	       String token;
	       int beginIndex = 0;
	       while((token = match(s.substring(beginIndex))) != null) {
	    	   System.out.println(token);
	    	   beginIndex += token.length();
	       }
	   }
 
	   public static String match(String s) {
	      int i = 0; char ch;
	      if(s == null || s.length() == 0)
	    	  return null;
	      String token = "";
	      if((ch =s.charAt(i++)) != '{') // not a valid start pattern
	    	  return null;
	      token += ch;
	      while(i < s.length()) {
	    	  ch = s.charAt(i);
	    	  if(ch == '}') { // end of top level {} pattern
	    		  token += ch;
	    		  return token;
	    	  }
	    	  else if(ch != '{') { // non bracket, add to the token
	    		  token += ch;
	    		  i++;
	    	  }
	    	  else { // nested {, so recursively match and concat sub-strings
	    		  String subtoken = match(s.substring(i));
	    		  if(subtoken != null) {
	    			  token += subtoken;
	    			  i += subtoken.length();
	    		  }
	    	  }
	      }
	      
	      return token;
	   }
}

Open in new window

0
 

Author Closing Comment

by:xanbi
ID: 31580846
Thank you very much.  I accepted ozo solution because I should use regular expression prior to making scan through the string.

Regards
0

Featured Post

Database Solutions Engineer FAQs

In this series, we will discuss common questions received as a database Solutions Engineer at Percona. In this role, we speak with a wide array of MySQL and MongoDB users responsible for both extremely large and complex environments to smaller single-server environments.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

A list of useful business intelligence software.
Invest in your employees with these five simple steps to improve employee engagement and retention.
The viewer will learn how to use NetBeans IDE 8.0 for Windows to connect to a MySQL database. Open Services Panel: Create a new connection using New Connection Wizard: Create a test database called eetutorial: Create a new test tabel called ee…
This is used to tweak the memory usage for your computer, it is used for servers more so than workstations but just be careful editing registry settings as it may cause irreversible results. I hold no responsibility for anything you do to the regist…

615 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question