# JCTools/JCTools

Repository: https://github.com/JCTools/JCTools
Canonical: https://ross.abutalabs.com/products/jctools
Homepage: http://jctools.github.io/JCTools
Language: Java
License: Apache-2.0
License Family: permissive
Topics: concurrency, data-structures, queues, lock-free, wait-free, awesome, java, benchmarks
Last push: 2026-08-18T14:28:40+00:00

## Health v2 (maintenance only)
Score: 90/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 98, release rhythm 74, longevity 100
- inputs: {"age_days": 4679, "days_push": 15, "days_rel": 15, "gap_med": 173, "n_releases_24m": 2}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3869, forks 591 (observed 2026-08-28T04:08:27.745970+00:00)

## What it is
JCTools is a Java library providing high-performance concurrent data structures missing from the JDK, notably lock-free and wait-free queue variants (SPSC/MPSC/SPMC/MPMC) plus non-blocking hash maps and concurrent counters. It is stable and widely used by frameworks such as Netty and RxJava.

## Use cases
- pass messages between threads with minimal contention
- replace JDK concurrent queues for higher throughput
- build single-producer single-consumer pipelines
- use lock-free hash maps in concurrent code
- batch drain and fill queue elements efficiently
- benchmark concurrent queue implementations

## When to choose
- you need maximum throughput inter-thread message passing on the JVM
- you want specialized SPSC/MPSC/SPMC/MPMC queue semantics
- you need wait-free or lock-free guarantees with bounded or unbounded queues
- you want a battle-tested library used by Netty and RxJava

## When to avoid
- your workload is low-contention and JDK queues suffice
- you need distributed or persistent queues rather than in-process ones
- you cannot tolerate sun.misc.Unsafe-based code and are stuck below JDK11

## Facets
- artifact type: library
- maturity: stable
- function: concurrency, data-science
- domain: developer-tools, performance
- platform: jvm
- tags: lock-free, wait-free, queues, data-structures, benchmarks, message-passing, algorithms

## Member repositories
- JCTools/JCTools (main) score 90

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:27.745970+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:25:49.378884+00:00, confidence not recorded.
  - readme: https://github.com/JCTools/JCTools (fetched 2026-08-28T04:08:27.745970+00:00, sha 77d0c97b5013)
  - homepage: http://jctools.github.io/JCTools (fetched 2026-08-29T09:20:02.205668+00:00, sha 59102a25842c)
- Data as of 2026-08-30T08:39:29.467469+00:00.