Random frequent server crashes

My server keeps crashing every few minutes or so. Most of the time it is recorded only as a Java error, but every once in a while, Minecraft Server spits out a crash report.

What I expected to happen was...:
The server to not crash.

What actually happened was...:
The server crashed

Steps to Reproduce:
1.Start vanilla server
2.play. (1-4 players generally)
3.wait for the inevitable