Is there a course that teaches you Memory allocation/efficient memory usage/stuff that is related to memory?

I don't know if the videos cover memory allocation. The limits of my knowledge on the topic (bit of a noob, sorry) are just to dereference when you finish with a variable, that you have limited control over the precise when of the garbage collector running, and that there a couple memory related methods on the Runtime class. And that there's a throwable error for running our of memory (OutOfMemoryError)

Derefencing the obj means setting the value of the object to null right?

I never done that before, mind elaborating how you do that/show me an example?

yep, once a variable has no remaining references, it should be a candidate for recycling. In some instances that might mean that the variable has gone out of scope (a local variable or a variable in a while/if block for example may die naturally for example) or this might mean you've set it to null.

String x = "i exist";
x = null;

{
    //brackets create a scope - this is a fairly artificial example.
   String y = "I exist";
}
//y is no longer accessible, hence can be recycled by collector

Given that the garbage collector doesn't run immediately, it's likely to be a bit difficult to observe the memory clearing for demonstration purposes. But it should free memory at intervals.

Makes sense! just wondering though, when will instance variables be collected for garbage collection, eg:

class Dog{
String dogName = "Brandon";

//Other code
}

I'm guessing after Java is done referencing and executing all the methods in Dog?

So if there are no methods, Java will collect Dog as garbage after I do this:

Dog nDog = new Dog();

and would method invocation in methods be store in heap/stack?

class Dog{
  void MethodOne(){
      methodTwo();
      String call = methodThree(); //This would be called in a stack, since this is a reference var, correct?
   }

  void methodTwo(){
    System.out.print(..);
   }
   String methodThree(){
     return "hey";
   }
}

I'd assume an instance variable dies when after there is no reference to the object it's on (ie. there is no theoretical way to access the object). As for the heap/stack stuff, i'm a little unsure. I saw http://programmers.stackexchange.com/questions/65281/stack-and-heap-memory-in-java , which might help.