For searching a string in a file and writing the lines with matched string to another file it takes 15 - 20 mins for a single zip file of 70MB(compressed state). Is there any ways to minimise it.

my source code:

getting Zip file entries

zipFile = new ZipFile(source_file_name);

entries = zipFile.entries();

while (entries.hasMoreElements())

{ ZipEntry entry = (ZipEntry)entries.nextElement();

if (entry.isDirectory()) 
{ 
continue; 
} 
searchString(Thread.currentThread(),entry.getName(), new BufferedInputStream (zipFile.getInputStream(entry)), Out_File, search_string, stats); }

zipFile.close();

Searching String

public void searchString(Thread CThread, String Source_File, BufferedInputStream in, File outfile, String search, String stats) throws IOException

{ 

    int count = 0; 
    int countw = 0; 
    int countl = 0; 
    String s; 
    String[] str; 
    BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); 
    System.out.println(CThread.currentThread()); 

        while ((s = br2.readLine()) != null) 
        { 
            str = s.split(search); 
            count = str.length - 1; 
            countw += count; //word count 
            if (s.contains(search)) 
            { 
            countl++;  //line count 
            WriteFile(CThread,s, outfile.toString(), search); 
            } 
        } 

    br2.close(); 
    in.close(); 


} 

--------------------------------------------------------------------------------

public void WriteFile(Thread CThread,String line, String out, String search) throws IOException

{ 
    BufferedWriter bufferedWriter = null; 
    System.out.println("writre thread"+CThread.currentThread()); 
    bufferedWriter = new BufferedWriter(new FileWriter(out, true)); 
    bufferedWriter.write(line); 
    bufferedWriter.newLine(); 
    bufferedWriter.flush(); 
} 

Please help me. Its really taking 40 mins for 10 files using threads and 15 - 20 mins for a single file of 70MB after being compressed. Any ways to minimise the time.