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set java_home permanently ubuntu

sudo gedit /etc/profile
#add following lines

JAVA_HOME=/usr/lib/jvm/{your jdk path}
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH
#logout to update the changes

set java home in ubuntu

Java is typically installed in /usr/java locate the version you have and then do the following:

Assuming you are using bash (if you are just starting off, i recommend bash over other shells) you can simply type in bash to start it.

Edit your ~/.bashrc file and add the paths as follows:

for eg. vi ~/.bashrc

insert following lines:

export JAVA_HOME=/usr/java/<your version of java>
export PATH=${PATH}:${JAVA_HOME}/bin

after you save the changes, exit and restart your bash or just type in bash to start a new shell

Type in export to ensure paths are right.

Type in java -version to ensure Java is accessible.