Put the summary of the bug you're having here

What I expected to happen was...:
I expected the server to take less than 2 gigabytes of RAM with nobody on.

What actually happened was...:
The server took 4 gigabytes of RAM with nobody on.

Steps to Reproduce:

1. Run a Minecraft server. Give it 6 gigabytes of memory. To run the plugin needed, you will require Bukkit or Spigot.
2. Install the plugin HeapDump.
3. Create a heap dump.
4. Look at the heap dump using the Eclipse Memory Analyzer. Please note that the dump will be large, and you will need at least 2 gigabytes of RAM to view it without it running out of memory.
5. Look at suspected leaks. For me it showed 4 leaks that all were related to java.net.URLClassLoader.
6. Get a few players on the server for a few hours. Have them do things like mine and build. Not sure if this will do anything, but try to have them localized in the same area, with one or two further away.
7. Wait for the server to run out of memory.
8. Crash time