题解 | #求int型正整数在内存中存储时1的个数#

十进制转二进制：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        // 十进制转二进制的JDK类库方法
        String str = Integer.toBinaryString(num);
        int length = str.length();
        String newStr = str.replaceAll("1", "");
        System.out.println(length - newStr.length());
    }
}