title: read the output from java exec
body: <p>Hello i have some question about java.
  here is my code:</p>
  
  <pre><code>public static void main(String[] args) throws Exception {
      Process pr = Runtime.getRuntime().exec("java -version");
  
      BufferedReader in = new BufferedReader(new InputStreamReader(pr.getInputStream()));
      String line;
      while ((line = in.readLine()) != null) {
          System.out.println(line);
      }
      pr.waitFor();
      System.out.println("ok!");
  
      in.close();
      System.exit(0);
  }
  </code></pre>
  
  <p>in that code i'am trying to get a java version command execute is ok, but i can't read the output it just return null. Why?</p>