title: Very slow to generate MD5 for large file using Java
body: <p>I am using Java to generate the MD5 hash for some files. I need to generate one MD5 for several files with a total size of about 1 gigabyte.
  Here's my code:</p>
  
  <pre><code>private String generateMD5(SequenceInputStream inputStream){
      if(inputStream==null){
          return null;
      }
      MessageDigest md;
      try {
          int read =0;
          byte[] buf = new byte[2048];
          md = MessageDigest.getInstance("MD5");
          while((read = inputStream.read(buf))&gt;0){
              md.update(buf,0,read);
          }
          byte[] hashValue = md.digest();
          return new String(hashValue);
      } catch (NoSuchAlgorithmException e) {
          return null;
      } catch (IOException e) {
          return null;
      }finally{
          try {
              if(inputStream!=null)inputStream.close();
          } catch (IOException e) {
              // ...
          }
      } 
  </code></pre>
  
  <p>}</p>
  
  <p>This seems to run forever.
  How can I make it more efficient?</p>