Top 4 Java Code Projects

opengrok

3 3,979 7.4 Java

OpenGrok is a fast and usable source code search and cross reference engine, written in Java

Project mention: Sourcegraph is no longer Open Source | news.ycombinator.com | 2023-07-04

[4] is not really a usable 'product'. Livegrep (https://github.com/livegrep/livegrep) was inspired by it and is very usable.
[3] used to be a Google open source project as well, but it fell out of maintenance, and Sourcegraph took it over. It powers most of the basic regex/literal search in Sourcegraph.
Mozilla's code is searchable in Searchfox (https://searchfox.org/) which uses the indexer from Livegrep, combined with their own Git indexer and language-specific cross reference databases.
OpenGrok (https://github.com/oracle/opengrok) is also rather well known, but I have found it to have a slightly worse UI than alternatives.
Code Scanner

0 1,031 1.8 Java

Code scanner library for Android, based on ZXing
Onboard AI

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Joo

0 3 1.8 Java

Joo is a clean, fast, static typed, general purpose programming language created to run on machines with extremely low resources like the Arduino UNO
ReactiveSpring

0 0 0.0 Java

Reactive Programming in Spring

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-07-04.