Java

What this skill does

Writes, debugs, and tunes Java and the JVM: nulls, equality, collections, generics, concurrency, streams, memory, builds, and upgrades. Use when Java throws NullPointerException, ClassCastException, ConcurrentModificationException, NoClassDefFoundError, NoSuchMethodError, UnsupportedClassVersionError or OutOfMemoryError, when a service deadlocks, hangs, burns CPU, or leaks memory, when equals/hashCode, Optional, generics, streams, or CompletableFuture misbehave, when dates shift or text turns into question marks, when Maven or Gradle resolves the wrong version or a fat jar fails only after packaging, when @Transactional does not roll back or an entity throws LazyInitializationException, when tests silently do not run, or when moving from Java 8 to 17/21+ and javax became jakarta. Also for choosing collections, sizing heap in containers, thread dumps, profiling, JDBC connection pools, HTTP timeouts, and logging setup. Not for Kotlin, Android app development, or JavaScript.

Java is part of the Developer Tools category — developer tools that help your agent write, review, debug, and ship code. You can install it on its own or alongside other developer tools skills from the OpenClaw catalog.

How to install Java

The easiest path is via the OpenClaw Easy desktop app — one click, no terminal required:

1. Download OpenClaw Easy for macOS or Windows (free, one-click installer, ~30 seconds).
2. Open the in-app Skills panel.
3. Search for java and click Install.
4. The skill activates automatically when an incoming message matches its description.

Install from the command line

If you already run the OpenClaw CLI, add Java with a single command:

openclaw skills add java

This pulls java from ClawHub and installs it into ~/.openclaw/skills/java/. Restart the OpenClaw gateway afterwards so the new skill is discovered.

How to use Java

Once installed, Java activates on its own: when an incoming message on WhatsApp, Telegram, Slack, Discord, Feishu or Line matches the skill's description, your OpenClaw agent loads it and runs the workflow. You can also trigger it explicitly by describing the task in chat. No extra configuration is required after install.

Manual install (advanced)

If you prefer manual installation:

1. Click the Download .zip button above to grab java-1.0.3.zip directly from our S3 mirror.
2. Unzip into ~/.openclaw/skills/java/ (create the directory if it does not exist).
3. Restart OpenClaw Easy (or the OpenClaw CLI gateway) so the new skill is discovered.

Frequently asked questions

How do I install Java?

Install Java in the OpenClaw Easy desktop app by opening the Skills panel, searching for java, and clicking Install. From a terminal you can run: openclaw skills add java. Either way the skill is placed in ~/.openclaw/skills/java/.

Is Java free?

Yes. Java is free and open-source, distributed under the Apache-2.0 license through ClawHub. No account or payment is required to download or run it.

What does Java do?

Writes, debugs, and tunes Java and the JVM: nulls, equality, collections, generics, concurrency, streams, memory, builds, and upgrades.

Related: more developer tools skills

If Java looks useful, you may also want to check out other developer tools skills in the OpenClaw catalog:

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Browse the full OpenClaw skill catalog

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