Does garbage collection guarantee that a program will not run out of memory?

 
Garbage collection does not guarantee that a program will not run out of memory. It is perfectly possible for a programmer to mistakenly create objects which never go out of scope, thus consuming more and more memory until all heap is exhausted.

It is the programmer’s responsibility to ensure that objects no longer in use are no longer referenced by the application. That way the garbage collector can do its job and reclaim memory used by these objects.

Automatic garbage collection only means that garbage (i.e., unreferenced memory) is automatically collected (i.e., reclaimed for further use). If you keep references to it, it’s not garbage, and not collected.