What is the BitSet.size() method in Java?

Overview

In Java, size() is a BitSet instance method that returns the total bit space that the BitSet object is currently using to represent bit values.

The BitSet class is defined in the java.util package. To import the BitSet class, we use the following statement.

import java.util.BitSet;

Syntax

public int size()

Parameters

This method has no parameters.

Return value

This method returns the number of bits currently in this bit set.

Example

import java.util.Arrays;
import java.util.BitSet;
public class Main{
    public static void main(String[] args) {
        // Create empty BitSet object
        BitSet bitSet = new BitSet();
        // Set the bit at index 2
        bitSet.set(2);
        // Set the bit at index 143
        bitSet.set(143);
        // Get the size of the Bitset object using the size()
        System.out.printf("%s.size() = %s" , bitSet, bitSet.size());
    }
}

Explanation

  • Lines 1–2: We import the relevant packages.
  • Line 8: We create an empty BitSet object bitSet.
  • Line 11: We set the bit at index 2.
  • Line 14: We set the bit at index 143.
  • Line 17: We print the size of the BitSet object defined in line 8 using the size() method.

By default, the size of the BitSet is 64 starting from 0 to 63. This means if we replace 143 with a value <=63 at line 14, we’ll get 64 because both bits lie in the same slot. However, setting it to 64 will result in 128. It means that the bit size is calculated in multiple of 64-bit slot, and it remains the same for the next 64 bits.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)