lucene/README.md

<!--
    Licensed to the Apache Software Foundation (ASF) under one or more
    contributor license agreements.  See the NOTICE file distributed with
    this work for additional information regarding copyright ownership.
    The ASF licenses this file to You under the Apache License, Version 2.0
    the "License"); you may not use this file except in compliance with
    the License.  You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 -->

# Apache Lucene

![Lucene Logo](https://lucene.apache.org/theme/images/lucene/lucene_logo_green_300.png?v=0e493d7a)

Apache Lucene is a high-performance, full featured text search engine library
written in Java.

[![Build Status](https://ci-builds.apache.org/job/Lucene/job/Lucene-Artifacts-main/badge/icon?subject=Lucene)](https://ci-builds.apache.org/job/Lucene/job/Lucene-Artifacts-main/)

## Online Documentation

This README file only contains basic setup instructions.  For more
comprehensive documentation, visit:

- Latest Releases: <https://lucene.apache.org/core/documentation.html>
- Nightly: <https://ci-builds.apache.org/job/Lucene/job/Lucene-Artifacts-main/javadoc/>
- Build System Documentation: [help/](./help/)

## Building with Gradle

### Basic steps:
  
  0. Install OpenJDK 11 (or greater up until version 15)
  1. Download Lucene from Apache and unpack it (or clone the git repository).
  2. Run gradle launcher script (`gradlew`).

### Step 0) Set up your development environment (OpenJDK 11 or greater)

We'll assume that you know how to get and set up the JDK - if you
don't, then we suggest starting at https://jdk.java.net/ and learning
more about Java, before returning to this README. Lucene runs with
Java 11 or later. 

Lucene uses [Gradle](https://gradle.org/) for build control. Gradle is itself Java-based
and may be incompatible with newer Java versions; you can still build and test 
Lucene with these Java releases, see help/tests.txt for more information.

NOTE: Lucene changed from Ant to Gradle as of release 9.0. Prior releases
still use Ant.

### Step 1) Checkout/Download Lucene source code

You can clone the source code from GitHub:

  https://github.com/apache/lucene
  
or get Lucene source archives for a particular release from:

  https://lucene.apache.org/core/downloads.html

Download either a zip or a tarred/gzipped version of the archive, and
uncompress it into a directory of your choice.

### Step 2) Run Gradle

Run "./gradlew help", this will show the main tasks that can be executed to 
show help sub-topics.

If you want to build Lucene, type:

```
./gradlew assemble
```

NOTE: DO NOT use `gradle` command that is already installed on your machine (unless you know what you'll do).
The "gradle wrapper" (gradlew) does the job - downloads the correct version of it, setups necessary configurations.

The first time you run Gradle, it will create a file "gradle.properties" that
contains machine-specific settings. Normally you can use this file as-is, but it
can be modified if necessary.

`./gradlew check` will assemble Lucene and run all validation
  tasks (including unit tests).

`./gradlew help` will print a list of help guides that help understand how
  the build and typical workflow works.

If you want to build the documentation, type:

```
./gradlew documentation
```

### Gradle build and IDE support

- *IntelliJ* - IntelliJ idea can import the project out of the box.
- *Eclipse*  - Basic support ([help/IDEs.txt](https://github.com/apache/lucene/blob/main/help/IDEs.txt#L7)).
- *Netbeans* - Not tested.

## Contributing

Bug fixes, improvements and new features are always welcome!
Please review the [Contributing to Lucene
Guide](https://cwiki.apache.org/confluence/display/lucene/HowToContribute) for information on
contributing.

## Discussion and Support

- [Users Mailing List](https://lucene.apache.org/core/discussion.html#java-user-list-java-userluceneapacheorg)
- [Developers Mailing List](https://lucene.apache.org/core/discussion.html#developer-lists)
- [Issue Tracker](https://issues.apache.org/jira/browse/LUCENE)
- IRC: `#lucene` and `#lucene-dev` on freenode.net