题解 | #求int型正整数在内存中存储时1的个数#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            //String binaryString=Integer.toBinaryString(a);
            String binaryString=int2Binary(a);
            int i=0;
            for(char c:binaryString.toCharArray()){
                if(c=='1'){
                    i++;
                }
            }
            System.out.println(i);
        }
    }
    public static String int2Binary(int in){
        int wei=1;
        int yushu=in%2;
        int shang=in/2;
        StringBuffer sb=new StringBuffer(String.valueOf(yushu));
        while(shang!=0){
            sb.append(shang%2);
            shang=shang/2;
            wei++;
        }
        
        return sb.reverse().toString();
    }
}