How to set JAVA_HOME in Linux for all users

Locating the Java installation directory

Java's installation may differ. Locate it this way:

find /usr/lib/jvm/ -name "java-*" -type d
# When you see too many Java versions, you know you're a serious Java-holic.
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Reflect the correct JAVA_HOME in previous steps.

Instantly updating JAVA_HOME

To apply modifications without relogging:

source /etc/profile
# Feel free to yell "Eureka!".
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For dynamically setting JAVA_HOME, add this to java_home.sh:

export JAVA_HOME=$(readlink -f /usr/bin/javac | sed 's:/bin/javac::')
# This is like having your cake and eating it too. 😋
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This keeps JAVA_HOME updated even post Java-upgrade.

Handling multiple versions of Java

If dealing with multiple Java incarnations, use update-alternatives managing symlinks to versions, pairing it with setting JAVA_HOME to:

update-alternatives --config java
# Because variety is the spice of life, right?
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Ensuring script's permissions

Scripts in /etc/profile.d/ require executable permissions:

sudo chmod +x /etc/profile.d/java_home.sh
# Because scripts too need their "armors".
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This ensures all users get Java environments.

Sync across profiles for uniform experience

JAVA_HOME has to be identical in .bashrc and /etc/profile for seamless user experience. To tweak .bashrc:

echo "export JAVA_HOME=$JAVA_HOME" >> ~/.bashrc
echo "export PATH=$PATH:$JAVA_HOME/bin" >> ~/.bashrc
source ~/.bashrc
# Congratulations, you just created an echo-chamber.
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This caters to interactive shells and user-specific bases.

Managing Java and Maven together

An incorrect JAVA_HOME can fire up Maven build errors. Check your Maven pointing to JAVA_HOME:

mvn -version
# Fingers crossed! 🤞
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It should resonate with Java path in JAVA_HOME.