What is the difference between Lists, ArrayLists, Maps, Hashmaps, Collections etc..?

Question

I\'ve been using HashMaps since I started programming again in Java without really understanding these Collections thing.

Honestly I am not really sure if using HashMaps

Answer 1

That is a question that ultimately has a very complex answer--there are entire college classes dedicated to data structures. The short answer is that they all have trade-offs in memory usage and the speed of various operations.

What would be really healthy is some time with a nice book on data structures--I can almost guarantee that your code will improve significantly if you get a nice understanding of data structures.

That said, I can give you some quick, temporary advice from my experience with Java. For most simple internal things, ArrayList is generally preferred. For passing collections of data about, simple arrays are generally used. HashMap is only really used for cases when there is some logical reason to have special keys corresponding to values--I haven't seen anyone use them as a general data structure for everything. Other structures are more complicated and tend to be used in special cases.