Downgrading Java 11 to java 8? [duplicate]

How can i downgrade the java version 11 to java 8. As i need jenkins, current jenkins versoin doesn't support java 11. I need to downgrade.

1. You have to install the openjdk-8-jre:

   sudo apt-get install openjdk-8-jre
   

2. Next switch to the jre-8 version:

   $ sudo 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-9-openjdk-amd64/bin/java       1500      auto mode
     1            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1500      manual mode
     2            /usr/lib/jvm/java-9-openjdk-amd64/bin/java       1500      manual mode
   

3. check java version:

   $ java -version
   openjdk version "1.8.0_151"
   OpenJDK Runtime Environment (build 1.8.0_151-8u151-b12-0ubuntu0.17.10.2-b12)
   OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode)
   

Same procedure for Oracle java.