import java.io.*;
class ReadFileUsingThread
{
    public void readFromFile(final String f, Thread thread) {
    Runnable readRun = new Runnable() {
      public void run() {
        BufferedWriter pw=null;
        FileInputStream in=null;
        String text = null;
        try{
            pw = new BufferedWriter(new FileWriter("C:/New/"+new File(f).getName()));
          Thread.sleep(5000);
          File inputFile = new File(f);
          in = new FileInputStream(inputFile);
          byte bt[] =  new byte[(int)inputFile.length()];
          in.read(bt);
          text = new String(bt);
          pw.write(text);
          pw.newLine();
          pw.close();
       } catch(Exception ex) {
       }  
      }
    };
    thread = new Thread(readRun);
    thread.start();
  }

    public static void main(String[] args) 
    {
        ReadFileUsingThread f=new ReadFileUsingThread();

        File file = new File("C:/Files/");
         FilenameFilter filter = new FileFilter();
        File[] files = file.listFiles(filter);
        Thread thread[]=new Thread[files.length];
        for(int i = 0; i < files.length; i++) {
           thread[i]=new Thread();
        f.readFromFile(files[i].getPath(),thread[i]);
        }
    }
}
class FileFilter implements FilenameFilter {
        public boolean accept(File dir, String name) {
                return name.endsWith("txt");
        }
 }

i did you example but it crashes with big file how come. i get this error

:Thread-1" java.lang.OutOfMemoryError: Java heap space