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Final review of Java on Cobalt 100 Learning Path #2351

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Sep 25, 2025
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Final review of Java on Cobalt 100 Learning Path #2351

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31 changes: 27 additions & 4 deletions content/learning-paths/servers-and-cloud-computing/java-on-azure/deploy.md
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,10 @@ java -version
javac -version
```

You should the JRE version printed:
You see the version information printed:

```output
aarch64
openjdk version "21.0.8" 2025-07-15
OpenJDK Runtime Environment (build 21.0.8+9-Ubuntu-0ubuntu124.04.1)
OpenJDK 64-Bit Server VM (build 21.0.8+9-Ubuntu-0ubuntu124.04.1, mixed mode, sharing)
Expand All @@ -41,24 +42,46 @@ OpenJDK 64-Bit Server VM (build 21.0.8+9-Ubuntu-0ubuntu124.04.1, mixed mode, sha
Check to ensure that the JDK is properly installed:

```console
echo $JAVA_HOME
which java
which javac
```
The output should look similar to:

```output
javac 21.0.8
/usr/bin/java
/usr/bin/javac
```

Set the Java Environment Variables to point to the root directory of your JDK installation:
Set the Java Environment Variables to point to the root directory of your JDK installation.

Use a text editor to edit the file `$HOME/.bashrc` and add the 2 environment variables.

```console
export JAVA_HOME=/usr/lib/jvm/java-21-openjdk-arm64
export PATH=$JAVA_HOME/bin:$PATH
```
Source the updated `$HOME/.bashrc` file.

```console
source ~/.bashrc
```

Confirm the new settings.

```console
echo $JAVA_HOME
which java
which javac
```

The output is:

```output
/usr/lib/jvm/java-21-openjdk-arm64
/usr/lib/jvm/java-21-openjdk-arm64/bin/java
/usr/lib/jvm/java-21-openjdk-arm64/bin/javac
```

{{% notice Note %}}
Ubuntu Pro 24.04 LTS provides OpenJDK 21 by default. Ensure your OpenJDK for Arm64 is **11.0.9 or newer** if you must run Java 11; releases before 11.0.9 can suffer performance issues due to false‑sharing cache contention. See the Arm community blog: [Java performance on Neoverse N1](https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/java-performance-on-neoverse-n1). You can also consult the [Arm Ecosystem Dashboard](https://developer.arm.com/ecosystem-dashboard/) for package guidance on Arm Neoverse Linux systems.
{{% /notice %}}
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