java中实现递归计算二进制表示中1的个数

借助java语言，运用递归算法计算整数n的二进制表示中1的个数

/*use the recursive algorithme to calculate 
 * the number of "1" in the binary expression
 * of an integer n.
 * note:if n is an odd, then
 * the result is the result of n/2 plus 1.
 * and the program use the bit operation to
 * improve efficency ,though it's seemingly
 * not necessary ,but the idea i think is good.
 * the program is writed by zewang zhang ,at
 * 2015-5-4,in sysu dorms.
 */
 
public class calculatenumberinbinaryexpression {
  //main method.
  public static void main(string[] args) {
     
    //for example ,make n equals 13 ,the result shows 3
    system.out.println(numofeven(13));
     
    //for example ,make n equals 128 ,the result shows 1
    system.out.println(numofeven(128));
  }
   
  //the static method of numofeven is the recursive method.
  public static int numofeven(int x) {
     
    //the base of recursive.
    if(x==0) {
      return 0;
    }
     
    //if x is an odd.
    else if(x%2!=0) {
      return numofeven(x>>1)+1;
    }
     
    //if x is an even except 0.
    else {
      while(x%2==0) {
        x=(x>>1);
      }
      return numofeven(x);
    }
  }
}

来个最简单的，不过未测试：）

public int a(int i){
    if(i==0||i==1) return i;
    return i%2+a(i/2);

}

以上所述就是本文的全部内容了，希望大家能够喜欢。