public static boolean isValidString(String check) {
		for(int i = 0; i < check.length(); i++) {
			char c = check.charAt(i);
			
			if(c == ' ' || c == '-' || c == '_') continue;
			if('0' <= c  && c <= '9') continue;
			if('a' <= c && c <= 'z') continue;
			if('A' <= c && c <= 'Z') continue;
			
			return false;
		}
		
		return true;
	}