Java in Linux

Q: How to identify JDK version?
A: For ex:
$ java -version
java version "1.7.0_181"
OpenJDK Runtime Environment (IcedTea 2.6.14) (7u181-2.6.14-0ubuntu0.3)
OpenJDK 64-Bit Server VM (build 24.181-b01, mixed mode)

(This is actually Java 1.7 = OpenJDK7 ~= OracleJDK7)

$ java -XshowSettings:properties -version

Q: How to install Java?
A:

$ sudo apt-get install default-jdk

# OpenJDK6

$ sudo apt-get install openjdk-6jdk

# OpenJDK7

$ sudo apt-get install openjdk-7jdk

# OracleJDK8

$ sudo add-apt-repository ppa:webupd8team/java

$ sudo apt-get update
$ sudo apt-get install oracle-java8-installer
$ sudo apt-get install oracle-java8-set-default