The flyweight pattern

Whenever we create a new object, extra memory needs to be allocated. Although virtual memory provides us, theoretically, with unlimited memory, the reality is different. If all the physical memory of a system gets exhausted, it will start swapping pages with the secondary storage, usually a hard disk drive (HDD), which, in most cases, is unacceptable due to the performance differences between the main memory and HDD. Solid-state drives (SSDs) generally have better performance than HDDs, but not everybody is expected to use SSDs. So, SSDs are not going to totally replace HDDs anytime soon.

Apart from memory usage, performance is also a consideration. Graphics software, including computer games, should be able to render 3-D information (for example, a forest with thousands of trees, a village full of soldiers, or an urban area with a lot of cars) extremely quickly. If each object in a 3-D terrain is created individually and no data sharing is used, the performance will...