loop until valid user input is received

	/**
	 * Remove '\n' and '\r' characters from string
	 */
	private String removeCRLF(String string) {
		return string.replace("\n", "").replace("\r", "");
	}
	
	/**
	 * Prints all possible guns the player can pick, gets user input, calls toLowerCase method
	 * on user input, and returns it if it matches that of a valid gun. 
	 * This function loops until a valid gun name is entered.
	 * @return Only returns the name of the gun (all lowercase) if it's a valid name
	 */
	public String getGunChoice() {
		String userInput = "";
		String[] options = {"pistol", "rifle", "shotgun"};
		while (userInput != (options[0]).toLowerCase() &&
					userInput != options[1].toLowerCase() &&
					userInput != options[2].toLowerCase()) {
			
			System.out.printf(
					"Enter the name of the gun you'd like to use.\n" +
					"Options: %s, %s, or %s\n", 
					options[0], options[1], options[2]);
			userInput = removeCRLF(keyboard.nextLine().toLowerCase().trim());
			System.out.println(userInput); // debug
		}
		return userInput;
	}