You have two ways for getting the details
http://www.mkyong.com/java/how-to-list-all-system-properties-key-and-value-in-java/
In case it is java parameters
Read Java JVM startup parameters (eg -Xmx)
From your updated response.
I will suggest that you check your memory manager.
In windows that will be task manager
mac that will be Activity Monitor
on linux you can fire top command from command line
Still not satisfied, check over this StackOverflow thread
Monitoring own memory usage by Java application
Still not satisfied. I would suggest profiling of the application using yourkit profiler or any other java profiler.
When you start yourkit it shows the java applications running. Simply click on one of it and it will initate profiling for you.