How to Run Multiple Versions of Java Simultaneously?

What methods can be used to run two different versions of Java at the same time on my machine?

# Example environment variable settings for different Java versions
export JAVA_HOME_8=/path/to/java8
export JAVA_HOME_11=/path/to/java11
export PATH=$JAVA_HOME_8/bin:$PATH # for Java 8

# Alternatively, for Java 11
export PATH=$JAVA_HOME_11/bin:$PATH

Running multiple versions of Java simultaneously can be essential for testing or development purposes where different projects require different Java versions. The following methods allow you to manage multiple installations and switch between them as needed.

# Example of creating a script to set JAVA_HOME and run a Java program
#!/bin/bash
export JAVA_HOME=/path/to/desired/java/version
export PATH=$JAVA_HOME/bin:$PATH
java -version # Check current version
java MyApplication

Causes

• Different applications require different Java versions.
• Conflicting project dependencies.
• Testing compatibility with older Java frameworks.

Solutions

• Install multiple Java versions using JDK installers.
• Use a version manager like SDKMAN! or jEnv to manage Java versions easily.
• Create batch files or shell scripts to set the JAVA_HOME environment variable and PATH temporarily before running your Java applications.

Mistake: Not setting the JAVA_HOME variable correctly.

Solution: Ensure the JAVA_HOME variable points to the correct JDK version and check for typos.

Mistake: Forgetting to update the PATH after switching Java versions.

Solution: Always confirm the PATH is set correctly after changing JAVA_HOME to avoid running the wrong Java version.