JDK 25 is the new long-term support release, which means it gets security patches and bug fixes until at least September 2033. If you’re still running JDK 17 or 21 in production, this is the next LTS worth upgrading to. Debian 13 (Trixie) ships OpenJDK 25 in its default repos, making the install trivial. Debian 12 (Bookworm) needs a bit more work since its repos only carry OpenJDK 17.
This guide covers three installation methods: OpenJDK from Debian repos, Oracle JDK from Oracle’s .deb package, and Eclipse Temurin from the Adoptium repository. It also walks through switching between multiple Java versions, setting JAVA_HOME correctly, testing JDK 25 features like compact source files and module imports, and configuring garbage collectors. All code blocks use real output from actual Debian systems.
Tested March 2026 on Debian 13.0 (Trixie) with OpenJDK 25.0.2+10 and Debian 12.13 (Bookworm) with Oracle JDK 25.0.2+10-LTS and Temurin 25.0.2+10
What’s New in JDK 25
JDK 25 was released on September 16, 2025, with the latest patch (25.0.2) landing on January 20, 2026. As an LTS release, it replaces JDK 21 as the recommended version for production workloads. The release includes 18 JEPs (Java Enhancement Proposals), with these being the most significant final features:
| JEP | Feature | Why It Matters |
|---|---|---|
| 506 | Scoped Values | Thread-safe context sharing, replaces ThreadLocal for virtual threads |
| 510 | Key Derivation Function API | Cryptographic API for generating secure keys from existing secrets |
| 511 | Module Import Declarations | Single import module java.base; replaces dozens of import lines |
| 512 | Compact Source Files | Write void main() {} without a class wrapper, great for scripts and learning |
| 513 | Flexible Constructor Bodies | Execute code before super() calls for argument validation |
| 514 | AOT Command-Line Ergonomics | Faster application startup via -XX:AOTCacheOutput |
| 519 | Compact Object Headers | Reduces object header from 128 to 64 bits, saving memory |
| 521 | Generational Shenandoah | Low-pause GC now separates young/old generations for better throughput |
For the complete list, see the OpenJDK 25 project page.
Prerequisites
- Debian 13 (Trixie) or Debian 12 (Bookworm)
- Root or sudo access
- 512 MB RAM minimum (1 GB+ recommended for compilation)
- 400 MB disk space for JDK installation
- Tested on: OpenJDK 25.0.2+10 (Debian 13), Oracle JDK 25.0.2+10-LTS (Debian 12), Temurin 25.0.2+10 (Debian 12)
Install OpenJDK 25 on Debian 13
Debian 13 includes OpenJDK 25 in its default repositories. No extra repos needed.
Update the package index:
sudo apt updateInstall the full JDK (compiler, runtime, and development tools):
sudo apt install -y openjdk-25-jdkIf you only need the runtime (no compiler or dev tools), install the JRE instead:
sudo apt install -y openjdk-25-jreVerify the installation:
java -versionThe version string confirms OpenJDK 25.0.2:
openjdk version "25.0.2" 2026-01-20
OpenJDK Runtime Environment (build 25.0.2+10-Debian-1deb13u2)
OpenJDK 64-Bit Server VM (build 25.0.2+10-Debian-1deb13u2, mixed mode, sharing)Check the compiler version too:
javac -versionOutput:
javac 25.0.2The JDK installs to /usr/lib/jvm/java-25-openjdk-amd64 and includes 30 tools: javac, jshell, jlink, jpackage, jwebserver, and more.
Install JDK 25 on Debian 12
Debian 12’s default repos only ship OpenJDK 17. For JDK 25, you have three options: Oracle JDK (official .deb package), Eclipse Temurin from the Adoptium repository, or a manual tarball install. The first two methods are covered here.
Option A: Oracle JDK 25
Oracle provides a .deb package that handles all the alternative registration automatically. Download it from Oracle’s servers:
wget https://download.oracle.com/java/25/latest/jdk-25_linux-x64_bin.deb -O /tmp/jdk-25.debInstall the package:
sudo dpkg -i /tmp/jdk-25.debThe .deb package registers itself with the alternatives system and sets Java 25 as the default. Verify it:
java -versionOracle’s build identifies itself differently from OpenJDK:
java version "25.0.2" 2026-01-20 LTS
Java(TM) SE Runtime Environment (build 25.0.2+10-LTS-69)
Java HotSpot(TM) 64-Bit Server VM (build 25.0.2+10-LTS-69, mixed mode, sharing)Oracle JDK installs to /usr/lib/jvm/jdk-25.0.2-oracle-x64. The Oracle NFTC license allows free use in production until September 2028.
Option B: Eclipse Temurin (Adoptium)
Temurin is an OpenJDK build maintained by the Eclipse Foundation under the Adoptium project. It gets regular updates and is fully open source under GPLv2.
Add the Adoptium GPG key and repository:
sudo apt install -y wget apt-transport-https gpg
wget -qO - https://packages.adoptium.net/artifactory/api/gpg/key/public | gpg --dearmor | sudo tee /usr/share/keyrings/adoptium.gpg > /dev/null
echo "deb [signed-by=/usr/share/keyrings/adoptium.gpg] https://packages.adoptium.net/artifactory/deb $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/adoptium.listUpdate the package index and install Temurin 25:
sudo apt update
sudo apt install -y temurin-25-jdkCheck the version:
java -versionTemurin’s version string includes the build identifier:
openjdk version "25.0.2" 2026-01-20 LTS
OpenJDK Runtime Environment Temurin-25.0.2+10 (build 25.0.2+10-LTS)
OpenJDK 64-Bit Server VM Temurin-25.0.2+10 (build 25.0.2+10-LTS, mixed mode, sharing)Temurin installs to /usr/lib/jvm/temurin-25-jdk-amd64. The Adoptium repo also provides Temurin 21, 17, 11, and 8 if you need older LTS versions alongside 25.
Set JAVA_HOME
Many build tools (Maven, Gradle, Ant) and application servers (Tomcat, WildFly) need JAVA_HOME to point to the JDK installation directory. Set it system-wide:
echo 'export JAVA_HOME=$(dirname $(dirname $(readlink -f $(which java))))' | sudo tee /etc/profile.d/java.sh
source /etc/profile.d/java.shThis approach dynamically resolves the path based on the current default Java, so it stays correct even when you switch versions. Verify it:
echo $JAVA_HOMEOn Debian 13 with OpenJDK 25:
/usr/lib/jvm/java-25-openjdk-amd64If you need a fixed path (common in systemd service files or CI pipelines), set it explicitly based on your installation:
| Distribution | JAVA_HOME Path |
|---|---|
| OpenJDK 25 (Debian 13) | /usr/lib/jvm/java-25-openjdk-amd64 |
| Oracle JDK 25 (Debian 12) | /usr/lib/jvm/jdk-25.0.2-oracle-x64 |
| Temurin 25 (Debian 12) | /usr/lib/jvm/temurin-25-jdk-amd64 |
Switch Between Multiple Java Versions
Debian’s update-alternatives system handles multiple Java installations cleanly. When you install OpenJDK 21 alongside 25, both register as alternatives.
On Debian 13, install OpenJDK 21 alongside 25:
sudo apt install -y openjdk-21-jdkList all registered Java installations:
sudo update-alternatives --list javaBoth versions appear:
/usr/lib/jvm/java-21-openjdk-amd64/bin/java
/usr/lib/jvm/java-25-openjdk-amd64/bin/javaSwitch to Java 21:
sudo update-alternatives --set java /usr/lib/jvm/java-21-openjdk-amd64/bin/java
sudo update-alternatives --set javac /usr/lib/jvm/java-21-openjdk-amd64/bin/javacConfirm the switch:
java -versionNow shows Java 21:
openjdk version "21.0.10" 2026-01-20
OpenJDK Runtime Environment (build 21.0.10+7-Debian-1deb13u1)
OpenJDK 64-Bit Server VM (build 21.0.10+7-Debian-1deb13u1, mixed mode, sharing)Switch back to Java 25:
sudo update-alternatives --set java /usr/lib/jvm/java-25-openjdk-amd64/bin/java
sudo update-alternatives --set javac /usr/lib/jvm/java-25-openjdk-amd64/bin/javacFor an interactive menu that lets you pick from all installed versions:
sudo update-alternatives --config javaRemember to switch both java and javac together, otherwise you’ll compile with one version and run with another.
Test JDK 25 Features
A quick way to verify that your JDK 25 installation is fully functional and taking advantage of new features.
Compact Source Files (JEP 512)
JDK 25 lets you write a Java file without the class boilerplate. Create a file with just a main() method:
cat > /tmp/Greet.java << "EOF"
void main() {
System.out.println("Compact source file works on Java " + System.getProperty("java.version"));
}
EOFRun it directly without compiling first:
java /tmp/Greet.javaOutput confirms the feature works:
Compact source file works on Java 25.0.2No public class, no String[] args, no compilation step. This is a production feature in JDK 25, not a preview.
Module Import Declarations (JEP 511, Preview)
Instead of importing java.util.List, java.util.Map, and every other class individually, you can import an entire module:
cat > /tmp/ModuleTest.java << "EOF"
import module java.base;
void main() {
List items = List.of("Java", "25", "LTS");
items.forEach(System.out::println);
}
EOF Since this is a preview feature, run it with --enable-preview:
java --enable-preview /tmp/ModuleTest.javaEach element prints on its own line:
Java
25
LTSJShell Interactive Testing
jshell is the built-in REPL for quick Java experiments:
echo 'System.out.println("JShell on JDK " + Runtime.version());' | jshell -qPrints the full runtime version:
jshell> JShell on JDK 25.0.2+10-Debian-1deb13u2Built-in Web Server
JDK 25 includes jwebserver, a minimal HTTP server for quick file serving during development:
jwebserver -p 8888 -b 0.0.0.0It serves the current directory on port 8888. Not meant for production, but handy for local testing and sharing files on a network. Press Ctrl+C to stop it.
Garbage Collector Configuration
JDK 25 defaults to the G1 garbage collector. Three production GCs are available, each suited to different workloads:
| GC | Flag | Best For |
|---|---|---|
| G1 (default) | -XX:+UseG1GC | General purpose, balanced throughput and latency |
| ZGC | -XX:+UseZGC | Sub-millisecond pause times, large heaps (multi-TB) |
| Shenandoah | -XX:+UseShenandoahGC | Low-pause with generational mode (new in JDK 25, JEP 521) |
Check which GC is active in your current JVM:
java -XX:+PrintFlagsFinal -version 2>&1 | grep "Use.*GC " | grep trueDefault output shows G1 enabled:
bool UseG1GC = true {product} {ergonomic}Enable the Generational Shenandoah GC (new in JDK 25) for workloads that need consistent low pauses:
java -XX:+UseShenandoahGC -XX:+PrintFlagsFinal -version 2>&1 | grep "UseShenandoahGC"OpenJDK vs Oracle JDK vs Temurin
| Aspect | OpenJDK (Debian) | Oracle JDK | Temurin (Adoptium) |
|---|---|---|---|
| Codebase | OpenJDK source | Same OpenJDK source | Same OpenJDK source |
| License | GPLv2 + Classpath | Oracle NFTC (free until Sep 2028) | GPLv2 + Classpath |
| Vendor string | Debian | Oracle Corporation | Temurin |
| VM name | OpenJDK 64-Bit Server VM | Java HotSpot(TM) 64-Bit Server VM | OpenJDK 64-Bit Server VM |
| Install path (Debian) | /usr/lib/jvm/java-25-openjdk-amd64 | /usr/lib/jvm/jdk-25.0.2-oracle-x64 | /usr/lib/jvm/temurin-25-jdk-amd64 |
| Debian 13 repo | Yes | No (manual .deb) | Via Adoptium repo |
| Debian 12 repo | No (only JDK 17) | No (manual .deb) | Via Adoptium repo |
| LTS patches | Debian security team | Oracle (requires NFTC/OTN) | Adoptium community |
All three builds produce identical bytecode and run the same applications. The choice comes down to licensing preferences and how you want to receive updates. For Debian 13, the default OpenJDK package is the simplest. For Debian 12, Temurin gives you the easiest update path via apt upgrade.
Uninstall or Downgrade
Remove OpenJDK 25 on Debian 13:
sudo apt remove --purge openjdk-25-jdk openjdk-25-jreRemove Oracle JDK 25 on Debian 12:
sudo dpkg --purge jdk-25Remove Temurin 25:
sudo apt remove --purge temurin-25-jdkAfter removing a Java version, check that the alternatives system updated correctly:
java -versionIf another version is still installed, it becomes the new default automatically.
Production Tips
Pin the JDK version in CI pipelines. Use the full path (/usr/lib/jvm/java-25-openjdk-amd64/bin/java) in systemd service files and CI configs instead of relying on update-alternatives. A system update that installs a newer JDK can silently change the default and break your application.
Set heap sizes explicitly. JDK 25's ergonomics pick 25% of system RAM for the heap by default. For containers, set -Xms and -Xmx to match the container's memory limit:
java -Xms512m -Xmx2g -jar app.jarEnable AOT caching for faster startup. JDK 25's AOT improvements (JEP 514) let you create a cache of compiled code that speeds up subsequent launches. Generate a cache with a training run, then use it in production:
java -XX:AOTCacheOutput=app.aot -jar app.jar
java -XX:AOTCache=app.aot -jar app.jarMonitor GC behavior. Enable GC logging to find the right collector and tuning for your workload:
java -Xlog:gc*:file=/var/log/app-gc.log:time,uptime,level,tags -jar app.jarFor applications like Java on Rocky Linux/AlmaLinux, the same JDK 25 features apply with different package names. If you're deploying Java web applications, see our guides on Java installation on Ubuntu/Debian for Ubuntu-specific instructions, or OpenJDK on Debian for an OpenJDK-focused walkthrough.
