How to Install Oracle JDK 8 on Debian Stretch 9 Easy Guide

Post Installation Setup

5. 5. Updating

   Finally, Update System Java to Oracle JDK 8
   Run All these Commands below:

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   sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8*/bin/java 1065

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   sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8*/bin/javac 1065

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   sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8*/bin/jar 1065

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   sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.8*/bin/javaws 1065

   Then to Check or Set the System Java Version in Use do:

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   sudo update-alternatives --config java

   To Switch of Java Version Just Enter the Selection Number on First, Column. :)

6. 6. Setting Up JAVA_HOME

   Finally, to Set Up JAVA_HOME User Environment Variable (Optional)
   And Edit the User’s Bash environment Configuration file:

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   nano $HOME/.bashrc

   And Append:

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   export JAVA_HOME=/usr/lib/jvm/jdk1.8[uX]

   Replace the [uX] Looking for the Installed Java 8 Version with:

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   ls /usr/lib/jvm/ | grep jdk1.8

   Ctr+x to Save & Exit from nano Editor :)
   To Load New Bash Config simply:

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   bash