Ubuntu 22.04
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OpenJDK 8 : Install
2022/08/29
 
Install OpenJDK 8.
[1] Install OpenJDK 8 and run a test program.
root@dlp:~#
apt -y install openjdk-8-jdk
root@dlp:~#
cat > /etc/profile.d/java.sh <<'EOF'
export JAVA_HOME=$(dirname $(dirname $(readlink $(readlink $(which java)))))
export PATH=$PATH:$JAVA_HOME/bin
EOF
root@dlp:~#
source /etc/profile.d/java.sh
root@dlp:~#
java -version

openjdk version "1.8.0_342"
OpenJDK Runtime Environment (build 1.8.0_342-8u342-b07-0ubuntu1~22.04-b07)
OpenJDK 64-Bit Server VM (build 25.342-b07, mixed mode)

# verify to create test program

root@dlp:~# cat > java_test.java <<'EOF'
class java_test {
    public static void main(String[] args) {
        System.out.println("Hello Java World !");
    }
}
EOF 

root@dlp:~#
javac java_test.java

root@dlp:~#
java java_test

Hello Java World !
[2] If you installed multiple version of Java from official repository, it's possbile to switch them with [update-alternatives].
root@dlp:~#
update-alternatives --config java

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-11-openjdk-amd64/bin/java      1111      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java to provide /usr/bin/java (java) in manual mode

root@dlp:~#
update-alternatives --config javac

There are 2 choices for the alternative javac (providing /usr/bin/javac).

  Selection    Path                                          Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/javac   1111      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/javac   1111      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/bin/javac    1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/javac to provide /usr/bin/javac (javac) in manual mode

root@dlp:~#
java -version

openjdk version "1.8.0_342"
OpenJDK Runtime Environment (build 1.8.0_342-8u342-b07-0ubuntu1~22.04-b07)
OpenJDK 64-Bit Server VM (build 25.342-b07, mixed mode)
root@dlp:~#
javac -version

javac 1.8.0_342
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