FileHandle file = Gdx.files.internal("test.txt"); - Reads 'test.txt' from the assets folder
String text = file.readString(); - Reads the entire text file
String[] a = text.split(System.lineSeparator()); - Splits the text file content to a string array line by line

Tutorial - https://libgdx.com/wiki/file-handling
(Look after file handling section)