code: private void persistCache(String projectName, String projectVersion, Map<String, String> cache) {
  		File cacheFile = new File(getCacheDir(), projectName + "/" + projectVersion);
  		ObjectOutputStream oos = null;
  		try {
  			oos = new ObjectOutputStream(new FileOutputStream(cacheFile));
  			oos.writeObject(cache);
  		}
  		catch (IOException ioe) {
  			LOGGER.warn("Unable to create the cache file {}/{}/{}", getCacheDir().getAbsoluteFile(), projectName, projectVersion);
  		}
  		finally { if (oos != null) { try { oos.close(); } catch (IOException ioe) {} } }
  	}
docs: Persist a specific cache
  
  @param projectName Project name
  @param projectVersion Project version
  @param cache The cache to persist