Why should I use a pointer rather than the object itself?

Question

I\'m coming from a Java background and have started working with objects in C++. But one thing that occurred to me is that people often use pointers to objects rather than t

Answer 1

There are many excellent answers already, but let me give you one example:

I have an simple Item class:

 class Item
    {
    public: 
      std::string name;
      int weight;
      int price;
    };

I make a vector to hold a bunch of them.

std::vector inventory;

I create one million Item objects, and push them back onto the vector. I sort the vector by name, and then do a simple iterative binary search for a particular item name. I test the program, and it takes over 8 minutes to finish executing. Then I change my inventory vector like so:

std::vector inventory;

...and create my million Item objects via new. The ONLY changes I make to my code are to use the pointers to Items, excepting a loop I add for memory cleanup at the end. That program runs in under 40 seconds, or better than a 10x speed increase. EDIT: The code is at http://pastebin.com/DK24SPeW With compiler optimizations it shows only a 3.4x increase on the machine I just tested it on, which is still considerable.