Reverse Bits of a 32-bit Number

/*
 * Problem : Reverse the 32 bits of a number.
 * Input   : One unsigned integer.
 * Output  : The reversed number.
 * Approach: Move the last bit of n to the end of the result.
 * Time    : O(32)
 * 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 long solve(long n) {
        // Step 1: The result starts as 32 zero bits. We use long, so the unsigned value fits.
        long result = 0;

        // Step 2: Repeat for all 32 bit positions.
        for (int i = 0; i < 32; i++) {
            // Step 3: Move the result one place to the left to make room.
            // Step 4: Put the last bit of n at the end of the result.
            result = (result << 1) | (n & 1);

            // Step 5: Drop the last bit of n.
            n = n >> 1;
        }
        return result;
    }

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