As a developer working with multiple projects that require different versions of Java, managing these versions can become cumbersome. This tutorial will guide you through the process of setting and changing the default Java version on macOS.
Understanding Java Versions on macOS
macOS comes with a built-in utility to manage Java versions, making it easier for developers to switch between different versions as needed. The /usr/libexec/java_home command is used to determine the path of the current Java version.
To view all installed Java versions, you can use the -V option:
/usr/libexec/java_home -V
This will list all the Java Virtual Machines (JVMs) installed on your system, along with their paths.
Setting a Specific Java Version
To set a specific Java version as the default, you can use the following command:
export JAVA_HOME=$(/usr/libexec/java_home -v <version>)
Replace <version> with the desired Java version (e.g., 1.8 or 11). This will set the JAVA_HOME environment variable to point to the specified Java version.
For example, to set Java 11 as the default:
export JAVA_HOME=$(/usr/libexec/java_home -v 11)
You can verify that the correct Java version is being used by running:
java -version
Making Changes Persistent
To make the changes persistent across shell sessions, you need to add the export command to your shell’s initialization file.
For Bash (default on older macOS versions):
echo "export JAVA_HOME=$(/usr/libexec/java_home -v <version>)" >> ~/.bash_profile
For zsh (default on newer macOS versions, including Catalina and later):
echo "export JAVA_HOME=$(/usr.libexec/java_home -v <version>)" >> ~/.zshrc
After adding the line to your shell’s initialization file, reload the file or restart your terminal for the changes to take effect:
source ~/.bash_profile # For Bash
source ~/.zshrc # For zsh
Switching Between Java Versions Easily
To make it easier to switch between different Java versions, you can create aliases in your shell’s initialization file. Here’s an example of how you can define aliases for various Java versions:
alias j8="export JAVA_HOME=$(/usr/libexec/java_home -v 1.8); java -version"
alias j11="export JAVA_HOME=$(/usr/libexec/java_home -v 11); java -version"
alias j17="export JAVA_HOME=$(/usr/libexec/java_home -v 17); java -version"
After defining these aliases, you can switch to a different Java version by simply typing the corresponding alias (e.g., j8, j11, or j17).
System-Wide Control
If you need to control the default Java version system-wide (not just in your shell), you can modify the Info.plist file of the desired Java version. To do this, navigate to the /Library/Java/JavaVirtualMachines directory and find the JDK version you want to set as the default.
Rename the Contents/Info.plist file to Contents/Info.plist.disabled for any JDK versions you don’t want to use as the default. The system will then use the highest version with an Info.plist file as the default Java version.
Conclusion
Managing multiple Java versions on macOS can be streamlined using the /usr/libexec/java_home command and shell aliases. By following these steps, you can easily switch between different Java versions and set a specific version as the default for your development needs.