code: private void sanitizeDiskCache() {
          File[] cachedFiles = new File(diskCacheDirectory).listFiles();
          if (cachedFiles == null) {
              return;
          }
          for (File f : cachedFiles) {
          	// if file older than expirationInMinutes, remove it
          	long lastModified = f.lastModified();
          	Date now = new Date();
          	long ageInMinutes = ((now.getTime() - lastModified) / (1000*60));
          	
          	if (ageInMinutes >= expirationInMinutes) {
          		Log.d(name, "DISK cache expiration for file " + f.toString());
          		f.delete();
          	}
          }
  	}
docs: Sanitize disk cache. Remove files which are older than expirationInMinutes.