If you want to know which GC algorithm is working with your JVM then you can follow below steps for this purpose,(Steps for windows)
1) -Open command prompt
2) - Type jconsole and hit enter (Make sure you have jdk installed on your machine)
3)- It will open Java monitoring and management console swing application.
4)- You can see all the listed process which are using jvm currently.Select any process and double click. The next screen will look like
5)- Now go to Mbeans Tab --> java.lang -->GarbageCollector- under this you can see the algo
