#### Brian Kernighan Algorithm

```package com.thealgorithms.others;

import java.util.Scanner;

/**
* @author Nishita Aggarwal
* <p>
* Brian Kernighan’s Algorithm
* <p>
* algorithm to count the number of set bits in a given number
* <p>
* Subtraction of 1 from a number toggles all the bits (from right to left) till
* the rightmost set bit(including the rightmost set bit). So if we subtract a
* number by 1 and do bitwise & with itself i.e. (n & (n-1)), we unset the
* rightmost set bit.
* <p>
* If we do n & (n-1) in a loop and count the no of times loop executes we get
* the set bit count.
* <p>
* <p>
* Time Complexity: O(logn)
*/
public class BrianKernighanAlgorithm {

/**
* @param num: number in which we count the set bits
* @return int: Number of set bits
*/
static int countSetBits(int num) {
int cnt = 0;
while (num != 0) {
num = num & (num - 1);
cnt++;
}
return cnt;
}

/**
* @param args : command line arguments
*/
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int num = sc.nextInt();
int setBitCount = countSetBits(num);
System.out.println(setBitCount);
sc.close();
}
}
```  