How can I return all line in a file that matches using regexp

Question

Hi!
I want to return whole line from a file. This lines must to contains matches for a pattern.
How Can I do this.
I make some samples, but only return the matches segment of the line.
Sample code to look for 00:00
If I put .*00:00.* in the pattern this return whole line, but is to slow in this file about 300,000 lines.
If I put just 00:00 in the pattern only return the 00:00, but so fast.
What can I Do, or I must use indexOf in a sequential read?
          try {
               // Create matcher on file
               Pattern pattern = Pattern.compile(".*00:00.*");
               Matcher matcher = pattern.matcher(fromFile("logusers_0712"));
               // Find all matches
               while (matcher.find()) {
                    // Get the matching string
                    String match = matcher.group();
                                 //Here I display the matches
                    System.out.println(match);
          } catch (IOException e) {
               e.printStackTrace();
          }Thanks in advance

Answer 1

My two cents:
Grep is a Bad Idea (TM). It is not java and itties
es the solution to a the operational system.Not necessarily bad. Like you say--we don't know much
about the OP's requirements, so grep may be just
fine.
!java != badYour assertion is true. But creating an solution tied to the system when you can do it pure java does not seem like a good Idea especially when we not even know which system he is using. What if he is using Windows or MacOS? Sure he can use grep on non *nix systems, but that would fore him to install the necessary tools, making his solution even more complex.
>
About using indexOf, it is a little limited, not
ot knowing what exactly the OP is searching for itis
difficult to say if it is enough. RegEx would workin
both ways.He said he was searching for "00:00". I think that was just a sample. He apears to be scanning a log file as far as I understood. 00:00 could be a timestamp for whose he wants to see the entries. Using a RegEx make the job easier, like "01:\\d{2} am" to get the whole range of entries inside that morning hour.
If it's really
that literal string he needs to match, as opposed to
say "\\d\\d:\\d\\d" then indexOf is simpler. It will
probably perform better too. I don't know if that
difference will be significant, but on a file of
300,000 lines, it might be noticable.The only way to know that is testing both solutions. But you are right, we are just wondering here, with no better info on the requirements anything can go. I agree with you, indexOf is the simple way to go and probably will sufice.
May the code be with you.