code: @Override
  	public void list(final PrintWriter out) {
  		lock.readLock().lock();
  		try {
  			properties.list(out);
  		} finally {
  			lock.readLock().unlock();
  		}
  	}
docs: /*
  (non-Javadoc)
  
  @see java.util.Properties#list(java.io.PrintWriter)