int?n;
System.out.print("輸入n:");
n?=?new?Scanner(System.in).nextInt();
System.out.printf("2n?=?%d%n",?2?*?n);
if?(n?>=?0?&&?n?<?31)?{
System.out.printf("2^%d?=?%s%n",?n,?Math.pow(2,?n));
}