I’m sorry but the forum’s just full of these how to render XYZ things, and when you already have your own dedicated thread for tilemaps why would you open a new one?
To get started with game development though you would need to know at least the basic containers (ArrayList, LinkedList, HashSet, HashMap, arrays and multidimensional arrays). Until you haven’t got that down we cannot help you.
About loading the tilemaps:
You have couple of different choices here and you should always go with the one that suits your game the best.
The most used tilemap designer tool is Tiled currently and it uses XML as it’s output file format.
But if you don’t like that or you want to add some extra (like make different tiles have different properties as Longarmx said) you have lots of other choices to convert to (or you can just modify the output XML file), like JSON or YAML.
You can also roll your own file format which isn’t as hard as it sounds but I wouldn’t recommend it seeing that Java has 3 ways of built-in XML parsing and it has nice JSON and YAML libraries.
The way to think about tiles is that they’re in a key-value relationship, ie. we can represent tiles using numbers and every number means a specific tile. Let’s say that 1 is water, 2 is dirt and 3 is sand and you have the following tilemap:
1 1 2 2
2 2 3 3
Than it means that the first row has: Water, water, dirt, dirt
Second row: Dirt, dirt, sand, sand
Simple as that.
About rendering the tilemaps:
My suggestion would be to first aim to make the easiest (that would be a 2D array with separate VBOs and textures for each tile if you’re using OpenGL) tilemap structure as possible and when you’re done with that and you can fully understand what you’re doing, start optimizing it. Optimization’s first step would be to put all of your tiles’ vertices into a single buffer, so with a 100x100 tilemap you would have only 1 draw command instead of 10000. The second step would be to start using a texture atlas instead of seperate textures to reduce the amount of texture binding calls. If you feel confident implement texture arrays so you can use multiple texture atlases if needed for rendering a tilemap (this isn’t really necessary, but who knows, it could come handy). Also try to implement layers (eg. add a 3rd dimension to the array, that would be Z or L).
If you want to get into the deep water you can check out my game engine’s Tiled XML parser and TileMap classes. It uses all the optimizations (except texture arrays) that I’ve mentioned above. 