Java Integer bitCount() Method (original) (raw)

Last Updated : 21 Jan, 2025

The **bitCount() method of Integer class of java.lang package returns the count of set bits in a positive number. For negative numbers, it returns the count of set bits in its 2s complement form. This function is sometimes referred to as the **population count.

**Syntax:

public static int bitCount(int n)

• **Parameter: n: the value whose bits are to be counted
• **Return: This method returns the count of set bits in a positive number. For negative numbers, it returns the count of set bits in its 2's complement form.

**Example 1: To show the working of **java.lang.Integer.bitCount() method.

java `

// Java program to demonstrate working // of java.lang.Integer.bitCount() method

import java.lang.Integer;

class Gfg { // driver code public static void main(String args[]) { int a = 10;

    // Convert integer number to binary  format
    System.out.println(Integer.toBinaryString(a));

    // to print number of 1's in the number a
    System.out.println(Integer.bitCount(a));
}

}

`

• **Time Complexity: O(1), because the number of bits is fixed (32 bits for int).
• **Auxiliary Space: O(1), as no extra space proportional to the input is used.

**Example 2:

Java `

import java.io.*;

class GFG { public static void main(String[] args) { int num1 = 10; // binary representation: 1010 int num2 = -10; // binary representation: // 11111111111111111111111111110110

    int result1 = Integer.bitCount(num1);
    int result2 = Integer.bitCount(num2);

    System.out.println("Number of one-bits in num1: "
                       + result1);
    System.out.println("Number of one-bits in num2: "
                       + result2);
}

}

`

Output

Number of one-bits in num1: 2 Number of one-bits in num2: 30

• **Time Complexity: O(1), because the number of bits is fixed (32 bits for int).
• **Auxiliary Space: O(1), as no extra space proportional to the input is used.