Understanding the Use of the Alternatives Command for Installing Java on Linux

What is the purpose of the alternatives command when installing Java on a Linux system?

sudo alternatives --config java

The alternatives command in Linux is a powerful utility used to manage different software versions installed on a system. When it comes to Java, this command is essential for managing multiple Java installations, allowing users to switch between different versions of Java seamlessly.

sudo alternatives --config java

# Output example:
# There are 2 choices for the alternative java (providing /usr/bin/java).
# 
# Selection    Path                                      Priority   Status
# ------------------------------------------------------------
# * 0          /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111      auto mode
#   1          /usr/lib/jvm/java-8-openjdk-amd64/bin/java    1081      manual mode
#   2          /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111      manual mode
# 
# Press <enter> to keep the current choice[*], or type selection number: 2
# Selecting '2' will set Java to version 11.

Causes

• Multiple versions of Java might be installed.
• Different applications may require different Java versions.

Solutions

• Use the command `sudo update-alternatives --config java` to select the desired Java version.
• Configure the environment variable `JAVA_HOME` to point to the selected Java version.

Mistake: Not running the alternatives command as root or with sudo permissions.

Solution: Always ensure to prepend the command with `sudo` to gain the necessary permissions.

Mistake: Forgetting to set the JAVA_HOME environment variable after switching versions.

Solution: After using the alternatives command, always set or export `JAVA_HOME` to reflect the new version.