Count Set Bits

/*
 * Problem : Count the 1 bits of a number.
 * Input   : One integer n >= 0.
 * Output  : The number of set bits.
 * Approach: Check bit by bit.
 * Time    : O(log n)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static int solve(long n) {
        // Step 1: The count starts at 0.
        int count = 0;

        // Step 2: Repeat while the number has bits left.
        while (n > 0) {
            // Step 3: n & 1 is the last bit (0 or 1). Add it to the count.
            count += (int) (n & 1);

            // Step 4: Shift right by 1 to drop the last bit.
            n = n >> 1;
        }
        return count;
    }

    public static void main(String[] args) {
        long n = new Scanner(System.in).nextLong();
        System.out.println(solve(n));
    }
}