code: private String findPathToGems() throws FileNotFoundException {
          String[] commandParams = cli.getCommandParams(GEM, ENVIRONMENT);
          List<String> lines = cli.runCmd(rootDirectory, commandParams);
          String path = null;
          if (!lines.isEmpty()) {
              path = lines.get(0) + fileSeparator + CACHE;
              if (new File(path).isDirectory() == false) {
                  throw new FileNotFoundException();
              }
          }
          return path;
      }
docs: Ruby's cache is inside the installation folder.  path can be found by running command 'gem environment gemdir'