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docs: Update JDK installation steps to use Java 25 #71

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35 changes: 18 additions & 17 deletions development/building/prerequisites.md
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Original file line number Diff line number Diff line change
Expand Up @@ -4,30 +4,30 @@

This page explains how to get the software you need to use on Linux or macOS for local development.

* `java 21` package or newer
* `Java 25` package or newer
* `git` installed
* `docker` installed

> Note: For contributing, you must have a github account to be able to raise PRs.
> Note: For contributing, you must have a GitHub account to be able to raise PRs.

#### For Linux

1. Install `OpenJDK 21` package or newer:
1. Install `OpenJDK 25` package or newer:

```bash
sudo apt update
sudo apt install openjdk-21-jdk
sudo apt install openjdk-25-jdk
```

* Check the java version using the command `java -version`.

```bash
openjdk version "21.0.5" 2024-10-15
OpenJDK Runtime Environment (build 21.0.5+8-Ubuntu-2ubuntu120.04)
OpenJDK 64-Bit Server VM (build 21.0.5+8-Ubuntu-2ubuntu120.04, mixed mode, sharing)
openjdk 25.0.1 2025-10-21
OpenJDK Runtime Environment (build 25.0.1+8-27)
OpenJDK 64-Bit Server VM (build 25.0.1+8-27, mixed mode, sharing)
```

Note: In case OpenJDK 21 is not set as your default Java, run
Note: In case OpenJDK 25 is not set as your default Java, run

```bash
sudo update-alternatives --config java
Expand All @@ -43,11 +43,12 @@ Selection Path Priority Status
2 /usr/lib/jvm/java-16-openjdk-amd64/bin/java 1051 manual mode
3 /usr/lib/jvm/java-17-openjdk-amd64/bin/java 1021 manual mode
4 /usr/lib/jvm/java-21-openjdk-amd64/bin/java 1001 manual mode
5 /usr/lib/jvm/java-25-openjdk-amd64/bin/java 1001 manual mode

Press <enter> to keep the current choice[*], or type selection number:
```

You can set it as the default by entering the selection number for it in the list and pressing Enter. For example, to set Java 21 as the default, you would enter "4" and press **Enter**.
You can set it as the default by entering the selection number for it in the list and pressing Enter. For example, to set Java 25 as the default, you would enter `5` and press <kbd>Enter</kbd>.

2. Install `git`:

Expand Down Expand Up @@ -83,10 +84,10 @@ sudo chmod 666 /var/run/docker.sock
brew cask
```

3. Install openjdk 21 via Homebrew:
3. Install openjdk 25 via Homebrew:

```bash
brew install openjdk@21
brew install openjdk@25
```

4. Verify Installation
Expand All @@ -95,22 +96,22 @@ brew install openjdk@21
java -version
```

Note: In case OpenJDK 21 is not set as your default Java, you can consider including it in your `$PATH` after installation
Note: In case OpenJDK 25 is not set as your default Java, you can consider including it in your `$PATH` after installation

```bash
export PATH="$(/usr/libexec/java_home -v 21)/bin:$PATH"
export JAVA_HOME="$(/usr/libexec/java_home -v 21)"
export PATH="$(/usr/libexec/java_home -v 25)/bin:$PATH"
export JAVA_HOME="$(/usr/libexec/java_home -v 25)"
```

If java\_home doesn't recognize homebrew installed java you can run below cmd to symlink brew installed java path to jvm
If java\_home doesn't recognize homebrew installed java you can run below cmd to symlink brew installed Java path to jvm

```bash
sudo ln -sfn $(brew --prefix openjdk@21)/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-21.jdk
sudo ln -sfn $(brew --prefix openjdk@21)/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-25.jdk
```

### Tips

Consider allocating not less than 4GB of memory for your docker. Otherwise, some apps within a stack (e.g. `kafbat-ui.yaml`) might crash.
Consider allocating at least 4GB of memory for your docker. Otherwise, some apps within a stack (e.g. `kafbat-ui.yaml`) might crash.

To check how much memory is allocated to docker, use `docker info`.

Expand Down