How to Install Java JDK in Kali Linux

Download the latest Java SE SDK version

Go to the following link and download jdk7. At the time of writing this guide the jdk version was jdk-7u45-linux-x64. Note that I’m using x64 which is 64-bit. 32-bit users should choose their versions accordingly. Not that tough really!
Following is what I’ve used. 

JDK-7u45-Linux-x64 

Again, at the time of writing this guide the available version was jdk-7u45-linux-x64.tar.gz
Download and save the file in /root directory.

UnTar the Archive and move to /opt

tar -xzvf /root/jdk-7u45-linux-x64.tar.gz
mv jdk1.7.0_45 /opt
cd /opt/jdk1.7.0_45

Install and register binaries

This step registers the downloaded version of Java as an alternative, and switches it to be used as the default:

update-alternatives --install /usr/bin/java java /opt/jdk1.7.0_45/bin/java 1
update-alternatives --install /usr/bin/javac javac /opt/jdk1.7.0_45/bin/javac 1
update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.7.0_45/jre/lib/amd64/libnpjp2.so 1
update-alternatives --set java /opt/jdk1.7.0_45/bin/java
update-alternatives --set javac /opt/jdk1.7.0_45/bin/javac
update-alternatives --set mozilla-javaplugin.so /opt/jdk1.7.0_45/jre/lib/amd64/libnpjp2.so

Test

First of all, close your browser and re-open. You won’t believe how many users actually forgets to do this step and later complains Java ain’t working. I’d advise to bookmark this site to be able to reopen these instructions quickly, or simply copy these into a leafpad/vi/text file.
To check the version of Java you are now running

java -version

To check the browser plugin just click Do I have Java?