Does Java do anything to prevent files from changing out from under it?

[Peter B. Kessler]

Does the Java platform do anything to prevent files from changing
out from under it?  E.g., once one has opened a jar file for class
loading, could a malicious (or oblivious) user write to the jar
file and disturb the VM?  Or is that all relegated to "the operating
system", file system permissions, etc.?

			... peter