A vector of bits backended with a byte array.

Bitmap.java

import java.util.Arrays;

public class Bitmap {

    private final byte[] _bitmap;

    public Bitmap(int size) {
        _bitmap = new byte[size];
    }

    public Bitmap(byte[] data) {
        _bitmap = Arrays.copyOf(data, data.length);
    }

    public void set(int index) {
        int chunk = index / 8;
        int bit = index % 8;
        _bitmap[chunk] |= 1 << bit;
    }

    public void clear(int index) {
        int chunk = index / 8;
        int bit = index % 8;
        _bitmap[chunk] &= ~(1 << bit);
    }

    public boolean get(int index) {
        int chunk = index / 8;
        int bit = index % 8;
        return (_bitmap[chunk] & 1 << bit) != 0;
    }

    public void flip(int index) {
        int chunk = index / 8;
        int bit = index % 8;
        _bitmap[chunk] ^= (1 << bit);
    }

    public byte[] toByteArray() {
        return Arrays.copyOf(_bitmap, _bitmap.length);
    }

    public String toString() {
        return Arrays.toString(_bitmap);
    }
}