where is environment variables in linux code example

Example 1: linux set environment variable

# Linux - Bash 

# syntax 
# export *<variable-name>=*<variable-value>;

# example 
export ORACLE_SID='sales_database';

Example 2: how to set environment variables in linux

export JAVA_HOME=/opt/openjdk11

Example 3: add environment variable linux

source ~/.bash_profile