How to Fix the JNI Error Occurred When Running a Java Program in Ubuntu?

What steps can I take to fix the JNI error that occurs when I run a Java program from the Ubuntu terminal?

The JNI (Java Native Interface) error typically indicates that there is an issue with your Java installation or the configurations required to run Java applications. This error can arise due to various reasons, including incorrect installation, version mismatches, or issues with environmental variables.

// Setting JAVA_HOME in .bashrc
// Open the file in a text editor
nano ~/.bashrc
// Add the following line
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
// Save and exit, then run this command to refresh
source ~/.bashrc

Causes

• Java is not installed on your system.
• Incorrect version of Java is installed (e.g., incompatible 32-bit vs 64-bit versions).
• Improper configuration of the `JAVA_HOME` environment variable.
• Missing or misconfigured JRE or JDK paths in the system settings.

Solutions

• Verify that Java is installed: Run `java -version` in your terminal to check the version.
• Ensure you have the correct version of Java (32-bit vs 64-bit). Use `sudo apt install default-jdk` to install the default JDK for your architecture.
• Set or correct the `JAVA_HOME` environment variable. You can do this by adding the following line to your `~/.bashrc` file: `export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64`. Then run `source ~/.bashrc` to apply changes.
• If you have installed multiple versions of Java, use `update-alternatives --config java` to select the default Java version.

Mistake: Not checking the installed Java version before executing a program.

Solution: Always verify the installed Java version with `java -version`.

Mistake: Forgetting to add `JAVA_HOME` to the environment variable, leading to JNI errors.

Solution: Ensure `JAVA_HOME` is correctly set to your Java installation path.

Mistake: Using a 32-bit version of Java on a 64-bit OS without configuring it correctly.

Solution: Install the correct Java version for your operating system architecture.