code: public String getMountPoint(AlluxioURI uri) throws InvalidPathException {
      String path = uri.getPath();
      String lastMount = ROOT;
      try (LockResource r = new LockResource(mReadLock)) {
        for (Map.Entry<String, MountInfo> entry : mState.getMountTable().entrySet()) {
          String mount = entry.getKey();
          // we choose a new candidate path if the previous candidatepath is a prefix
          // of the current alluxioPath and the alluxioPath is a prefix of the path
          if (!mount.equals(ROOT) && PathUtils.hasPrefix(path, mount)
              && PathUtils.hasPrefix(mount, lastMount)) {
            lastMount = mount;
          }
        }
        return lastMount;
      }
    }
docs: Returns the closest ancestor mount point the given path is nested under.
  
  @param uri an Alluxio path URI
  @return mount point the given Alluxio path is nested under
  @throws InvalidPathException if an invalid path is encountered