Also, there are other software like Oracle, and packages of Oracle come up with their own Java. For example, if you install those software on your Pc, you'll find another Java is installed for those. So, you are dealing with another java.
Sometime you may need to specify the exact Java(when all are different version). That case you can use the linux's locate command to find all the java bin directory.
This command will display you all the directories consist with '/bin/java'. So from that list, you can easily identify all the Java bins. Now you can pick your one.