JAVA help (not trolling) (pls)

I'm trying to read in a list of strings of characters A, C, G,and T (ignoring case), and to ignore the rest of the string if it contains any other character.

how do I code this? do I use indexOf?

V new to Java yes. Not trolling just need help quickly.

>>18
So the OP just wants the letters A, a, C, c, G, g, T, t?  If so, I guess the Java solution would become like...

 http://pastebin.com/ZnQHV8hN