Where is my jdk located Linux?

Alternatively, you can use the whereis command and follow the symbolic links to find the Java path. The output tells you that Java is located in /usr/bin/java. Inspecting the directory shows that /usr/bin/java is only a symbolic link for /etc/alternatives/java.

How do I know where my jdk is installed?

Start menu > Computer > System Properties > Advanced System Properties. Then open Advanced tab > Environment Variables and in system variable try to find JAVA_HOME. This gives me the jdk folder.