Check out example codes for "could not find java; set JAVA_HOME or ensure java is in PATH". It will help you in understanding the concepts better.

Code Example 1

After reading the docs from ElasticSearch,
I found that if you're running on Ubuntu or Debian,
the package only ships with the OpenJDK because of licensing issues.
To fix this Java path problem, I installed the following
after installing ElasticSearch (as directed by the docs):

	sudo add-apt-repository ppa:webupd8team/java
	sudo apt-get update
	sudo apt-get install oracle-java8-installer
	java -version
Then upon running
sudo service elasticsearch start
everything worked and I had no more Java path issues.

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