Java Exercises: 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.


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);
        return ctr;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
		System.out.print("Input a number: ");
        int num = sc.nextInt();

Sample Output:

Input a number:  1427


Flowchart: Count the number of set bits in a 32-bit integer.

Java Code Editor:

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Java: Tips of the Day

Count the number of occurrences of a char in a String:

int count = StringUtils.countMatches("a.b.c.d", ".");

Ref: https://bit.ly/2OTy6sG