code: private List<File> loadFromCache(Properties props) {
          String ts = props.getProperty("timestamp");
          if (ts==null)   return null;
  
          long timestamp = Long.valueOf(ts);
          if (isStale(timestamp))
              return null;
  
          List<File> files = new ArrayList<File>();
  
          for (Object k : props.keySet()) {
              String key = k.toString();
              if (key.startsWith("pom.")) {
                  File f = new File(props.getProperty(key));
                  if (!isUpToDate(f,timestamp))
                      return null;
              }
              if (key.startsWith("jar.")) {
                  File f = new File(props.getProperty(key));
                  if (!isUpToDate(f, timestamp))
                      return null;
                  files.add(f);
              }
          }
  
          return files;
      }
docs: Loads a list of jars from the cache, with up-to-date check.
  
  @return null if the data is stale