code: private static Long getUpdatedStamp(String absPath, File file) {
          String methodName = "getUpdatedStamp";
          boolean doDebug = tc.isDebugEnabled();
  
          Long currentStamp = Long.valueOf( file.lastModified() );
  
          Long newStamp;
          String newStampReason = null;
  
          synchronized ( expansionStamps ) {
              Long priorStamp = expansionStamps.put(absPath, currentStamp);
  
              if ( priorStamp == null ) {
                  newStamp = currentStamp;
                  if ( doDebug ) {
                      newStampReason = "First extraction; stamp [ " + currentStamp + " ]";
                  }
              } else if ( currentStamp.longValue() != priorStamp.longValue() ) {
                  newStamp = currentStamp;
                  if ( doDebug ) {
                      newStampReason = "Additional extraction; old stamp [ " + priorStamp + " ] new stamp [ " + currentStamp + " ]";
                  }
              } else {
                  newStamp = null;
                  if ( doDebug ) {
                      newStampReason = "No extraction; stamp [ " + currentStamp + " ]";
                  }
              }
          }
  
          if ( doDebug ) {
              Tr.debug(tc, methodName + ": " + newStampReason);
          }
          return newStamp;
      }
docs: Tell if a file should be expanded by answering the updated time stamp
  of the file.
  
  If the file was previously expanded during this JVM run, and the file
  time stamp is the same as when the file was expanded, answer null.
  
  If either the file was not yet expanded during this JVM run, or if the
  the current file time stamp is different than the time stamp of the file
  when it was expanded, update the recorded time stamp, and answer the new
  time stamp.
  
  @param absPath The absolute path of the file which is to be tested.
  @param file The file which is to be tested.
  
  @return The new time stamp of the file, if the file is to be expanded.
  Null if the file is not to be expanded.