what's more efficient? to empty an object or create a new one?

Question

how expensive is \'new\'? I mean, should I aim at reusing the same object or if the object is \'out of scope\' it\'s the same as emptying it?

example, say a method crea

Answer 1

how expensive is 'new'?

It definitely incurs some overhead. But it depends on how complex the object is. If you are creating an object with just few primitives, not that expensive. But if you are creating objects inside objects, may be collections of objects, if your constructor is reading some properties file to initialize object's member variables, EXPENSIVE!

But to be frank, if we need to create a new object, we have create it, there is no alternative. And if we don't need to and if we are still creating that is kind of bad programming.

at the end of the method the list is no longer in use - does it mean that there's no memory allocated to it anymore or does it mean that there's a null pointer to it (since it was 'created').

Once the object does not have any reference to it, it becomes out of scope, and it becomes eligible for garbage collection. Hence even if it has some memory allocated, it will be reclaimed by the GC at some later point, whenever it runs, we need not worry about it. (And we cannot guarantee when will GC run).

Emptying the collection at the end, I don't think will make things any better, because the same thing will happen to all the individual objects in the collection, as what happens to the collection itself. They will become eligible for GC.