Scanner console = new Scanner(System.in); long bytes; char units; bytes = console.nextLong(); units = console.next().toLowerCase().charAt(0); switch (units) { case 't': bytes *= 1024; case 'g': bytes *= 1024; case 'm': bytes *= 1024; case 'k': bytes *= 1024; break; default: bytes = 0; break; } if (bytes != 0) { System.out.println(bytes); }