@JRubyMethod
      public IRubyObject compute_if_present(final ThreadContext context, final IRubyObject key, final Block block) {
        IRubyObject result = map.computeIfPresent(key, new ConcurrentHashMap.BiFun<IRubyObject, IRubyObject, IRubyObject>() {
          @Override
          public IRubyObject apply(IRubyObject key, IRubyObject oldValue) {