How can i install JCE?

Openjdk comes already installed with JCE

A quick test to see if you have the JCE Unlimited Strength Jurisdiction Policy files installed:

$JAVA_HOME/bin/jrunscript -e 'print (javax.crypto.Cipher.getMaxAllowedKeyLength("RC5") >= 256);'

The command should return true if JCE is installed.

You can get them at this PPA

sudo add-apt-repository ppa:webupd8team/java
sudo apt update
sudo apt install oracle-java7-unlimited-jce-policy 

How can you tell if it is installed? This command will succeed :)

For a more upto date Java 8 version run

sudo apt install oracle-java8-installer