# Java: Count the number of set bits in a 32-bit integer

## Java Basic: Exercise-249 with Solution

From Wikipedia,
The Hamming weight of a string is the number of symbols that are different from the zero-symbol of the alphabet used. It is thus equivalent to the Hamming distance from the all-zero string of the same length. For the most typical case, a string of bits, this is the number of 1's in the string, or the digit sum of the binary representation of a given number and the ℓ norm of a bit vector. In this binary case, it is also called the population count, popcount, sideways sum, or bit summation.

Example:

String Hamming weight
11101 4
11101000 4
00000000 0
789012340567 10
Write a Java program to count the number of set bits in a 32-bit integer.

Sample Solution:

Java Code:

``````import java.util.Scanner;

public class solution {

static int count_Set_Bits(int num) {
int ctr = 0;
while (num != 0) {
num = num & (num - 1);
ctr++;
}
return ctr;
}
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("Input a number: ");
int num = sc.nextInt();
System.out.println(count_Set_Bits(num));
sc.close();
}
}
```
```

Sample Output:

```Input a number:  1427
6
```

Flowchart: Java Code Editor: