@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) {