1 import java.util.Scanner; 2  3 /** 4  * 功能：用位运算，实现乘法运算，但仅限于乘数是偶数。 5  */ 6 public class Main2 { 7  8     public int powerN(int m, int n) { 9         while (n > 0) {10             m = m << 1;11             n--;12         }13         return m;14     }15 16     public static void main(String[] args) {17 18         Main2 main2 = new Main2();19         Scanner scanner = new Scanner(System.in);20 21         int input = 0;22         int n = 0;23 24         while (scanner.hasNext()) {25             input = scanner.nextInt();26 27             if (input == 0 || input % 2 == 1) {28                 System.out.println("the intput value is invalid!");29                 continue;30             }31 32             n = 0;33 34             while (input != 1) {35                 n++;36                 input = input / 2;37             }38 39             System.out.println(main2.powerN(2, n));40         }41     }42 }