I'm looking to get into 3d game development on the side (im a computer science major) I'd like to use either C++ or Java (the 2 ive studied) and I'm just wondering how to go about making a player (a rectangle or anything easy to model) in 3rd person that can move forward, backward, left, right, and jump, (use the mouse to control the camera and the turning) around a simple box shaped room...where do i start with this?!? what tools do i need etc...i'd like to work on creating my own engine. any advice would be appreciated, thanks!

First, what you're describing doesn't need an 'engine' at all. All you need is some basic patched together work with windows programming and a 3d api. Java could do it in very little code.. but it would be java.

Secondly, You start by realizing that as a person who is brand new to game development, that you do not have the experience to make judgments about what is required in a game engine, and you forget about the engine entirely for the time being and focus on a game instead [I'm sure someone will be posting the link to 'write games not engines' in short order]. Making a game engine is tough, time consuming, and requires a lot of knowledge about what is going to be needed by a game.

Skip the engine [or download one that is already made. irrlicht can do what you describe in less than 2 page of code], and make a game instead that implements only what it needs. After you get a few games under your belt, you'll be in a position to state what should and should not be in an engine, and how such a thing should fit together.

http://scientificninja.com/advice/write-games-not-engines

i am not trying to make a game engine...im trying to figure out how to do specific things that i can reuse. ive decided to do a 2d project first and i'd like to make a big black space (a room) and a white dot (a player) that i can move around.
i'd like to use Java since it's what im most familiar with currently (i have not coded C++ in a year or two and all my current class work is in java) so ill try to fix my question to be more obvious as maybe i stated wrong... where do i start?? i'm asking maybe for someone to make a list of steps to take to accomplish the above mentioned and I can research each individual task. (break the project into smaller more manageable tasks) also i asked what programs do i need for this? anybody know of a free java compiler?

I think reading tutorials would help lots!

I'm not particular sure which one, but you could try reading the Nehe tutorials.

After reading a few tutorials, a light bulb should go off in your head, you will know how to go about doing what you just described.

Brush up on your linear algebra.

Then buy a few books.

At the same time, take a intro graphics course at your college.

Pay attention in required math class for C.S (e.g Calculus I,II,III, Linear Algebra, Ordinary Differential Equations etc), they will definitely help with game programming.