title: Java reading long text file is very slow
body: <p>I have a text file (XML created with XStream) which is 63000 lines (3.5 MB) long. I'm trying to read it using Buffered reader:</p>
  
  <pre><code>                BufferedReader br = new BufferedReader(new FileReader(file));
                  try {
                      String s = "";
                      String tempString;
                      int i = 0;
                      while ((tempString = br.readLine()) != null) {
                          s = s.concat(tempString);
  //                        s=s+tempString;
                          i = i + 1;
                          if (i % 1000 == 0) {
                              System.out.println(Integer.toString(i));
                          }
                      }
                      br.close();
  </code></pre>
  
  <p>Here you can see my attempts to measure reading speed. And it's very low. It takes seconds to read 1000 lines after 10000 line. I'm clearly doing something wrong, but can't understand what. Thanks in advance for your help.</p>