Calculating the Checksum of a Byte Array 

 
 public static long checksum(byte[] buf) {
     try {
         CheckedInputStream cis = 
           new CheckedInputStream(new
             ByteArrayInputStream(buf),
               new Adler32());
     
         byte[] tempBuf = new byte[128];
         while (cis.read(tempBuf) >= 0) {
         }
         return cis.getChecksum().getValue();
     } catch (IOException e) {
         return -1;
     }
  }