OpenGL Shaders not working

So… In my personal framework for LWJGL 3 (that I started yesterday), I tried to implement shaders. I’m all new to this shader Modern OpenGL thing, and I know OpenGL only for about half of a year, so I expected some mistakes. However, the code that I have should work, but it doesn’t. My problem is: I’m drawing a triangle to screen, and I’m trying to change it’s color using GLSL. But the triangle stays white. No matter what I do, it stays white. I spent about two hours trying to fix it, looking for any errors in OpenGL, browsing through the Internet, but nothing. Everything seems perfect. Except the god-damn triangle.

So, hope you guys can help me.
Here’s my code related to shaders (sorry, it’s a “little” messy):
(Main.java) http://pastebin.com/S8tQbjkZ
(Shader.java) http://pastebin.com/NQUq9ZsU
(vert.glsl) http://pastebin.com/0MjS4F94
(frag.glsl) http://pastebin.com/6Znfd6bV

(Window.java) http://pastebin.com/JXsnFjYB (I don’t think it’s really important, but all the basic OpenGL stuff is there, so, yeah)

Thanks in advance.