Question

I am working on a project where i have to parse through text files and pull relevant information from them to work with later.

I have created a regular expression to match the lines of text that have the relevant data, but I’m unsure how to pull the relevant information from the line and dump it into a new text file.

Here’s a sample from the text file i’m parsing:

[  5] local 10.170.150.195 port 42507 connected with 184.72.63.139 port 5001
[  4] local 10.170.150.195 port 42506 connected with 184.72.63.139 port 500
[  1]  0.0- 1.0 sec  0.00 KBytes  50.00 Kbits/sec

In this sample the relevant information is “0.0- 1.0 sec” and 50.00 Kbits/sec.

Here’s my regular expression:

[  [0-6]]  0.0- 1.0 sec  0.00 KBytes  [0-9]*.[0-9][0-9] Kbits/sec

Sorry if this is a trivial question, I’m fairly new to java…this is day 3…
Any and all help would be greatly appreciated.

Thank You

Answer 1

1. Open your input file using FileReader/BufferedReader.

   FileReader fr = new FileReader("input.txt");
   BufferedReader br = new BufferedReader(fr);
   

2. Open your output file using FileWriter/BufferedWriter

   FileWriter fw = new FileWriter("output.txt");
   BufferedWriter bw = new BufferedWriter(fw);
   

3. Read one line at a time in while loop using Buffered reader into a String

   String lineString = null;
   while((lineString= br.readLine())!= null){
         //....
    }
   

4. Within while loop, match the read string against your regex

   Pattern pattern = 
   Pattern.compile("\\[  [0-6]\\]  (0.0- 1.0 sec)  0.00 KBytes  ([0-9]*.[0-9][0-9] Kbits/sec)");
   Matcher matcher = pattern.matcher(lineString);
   if(matcher .matches()){
      //....
   }
   

5. If match found, write the string in output file using you Buffered writer

       bw.write(lineString);
   

6. Close all the readers/writers open.

       bw.close();
       fw.close();
       br.close();
       fr.close();
   

EDIT: Sample code style 1 as below:

    String regex = "\\[  [0-6]\\]  (0.0- 1.0 sec)  0.00 KBytes  ([0-9]*.[0-9][0-9] Kbits/sec)";
    FileReader fr = new FileReader("input.txt");
    BufferedReader br = new BufferedReader(fr);

    FileWriter fw = new FileWriter("output.txt");
    BufferedWriter bw = new BufferedWriter(fw);

    String lineString = null;
    while((lineString= br.readLine())!= null && 
                  !lineString.equals("Starting Test 2: Iperf TCP East....")){
        if(lineString.matches(regex)){
            bw.write(lineString);
        }
    }
    bw.close();
    fw.close();
    br.close();
    fr.close();

Sample Code Style 2 as below:

 FileReader fr = new FileReader("input.txt");
 BufferedReader br = new BufferedReader(fr);
 FileWriter fw = new FileWriter("output.txt");

 BufferedWriter bw = new BufferedWriter(fw);

 Pattern pattern = 
    Pattern.compile("\\[  [0-6]\\]  (0.0- 1.0 sec)  0.00 KBytes  ([0-9]*.[0-9][0-9] Kbits/sec)");

    String lineString = null;
    while((lineString= br.readLine())!= null && !lineString.equals("Starting Test 2: Iperf TCP East....")){
        Matcher matcher = pattern.matcher(lineString);
        if(matcher.matches()){
            bw.write(lineString);
        }
    }
    bw.close();
    fw.close();
    br.close();
    fr.close();

All the best!