Question

I heard most elegant property of java is Garbage Collection
I wanna know does it guarantee that a program will not run out of memory?

Answer 1

No it does not guarantee this. It is perfectly possible for a programmer to mistakingly 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.

Example

public class Main {
  public static void main(String[] main) {
    List<String> l = new LinkedList<String>();

    // Enter infinite loop which will add a String to
    // the list: l on each iteration.
    do {
      l.add(new String("Hello, World"));
    } while(true);
  }
}