Half-baked BitSet using byte[] rather than long[]

gistfile1.java

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

public class VerticaBinaryFormatBitSet {
	private static final byte ZERO = (byte)0;
	private byte[]	bytes;
	private boolean dirty = false;
	private int numBits;
	private int numBytes;

	public VerticaBinaryFormatBitSet(int numBits) {
		this.numBits = numBits;
		this.numBytes = (int) Math.ceil((double) numBits / 8.0d);
		bytes = new byte[this.numBytes];
	}

	public void setBit(int bitIndex) {
		if (bitIndex < 0 || bitIndex >= numBits) {
			throw new IllegalArgumentException("Invalid bit index");
		}

		int byteIdx = (int) Math.floor((double) bitIndex / 8.0d);

		int bitIdx = bitIndex - (byteIdx * 8);
		bytes[byteIdx] |= (1 << bitIdx);
		
		dirty = true;
	}

	public boolean isDirty() {
		return dirty;
	}
	
	public void clear() {
		if (dirty) {
			for (int i = 0; i < numBytes; i++) {
				bytes[i] = ZERO;
			}
			dirty = false;
		}
	}
	
	public byte[] toBytes() {
		return bytes;
	}

	public byte[] toLittleEndianBytes() {
		ByteBuffer buf = ByteBuffer.allocate(bytes.length);
		buf.put(bytes);
		return buf.order(ByteOrder.LITTLE_ENDIAN).array();
	}

	public int numBytes() {
		return bytes.length;
	}
	
	public void writeBytes(ByteBuffer buf) {
		buf.put(bytes);
	}
	public void writeBytes(int index, ByteBuffer buf) {
		for (int i = index; i < (index + bytes.length); i++) {
			buf.put(i, bytes[i]);
		}
	}
	
	public String toLittleEndianBinaryString() {
		StringBuilder sb = new StringBuilder();
		for (byte b : this.toLittleEndianBytes()) {
			sb.append(byteToLittleEndianBinaryString(b)).append(" ");
		}

		return sb.toString();
	}

	public static String byteToLittleEndianBinaryString(byte n) {
		StringBuilder sb = new StringBuilder("00000000");
		for (int bit = 7; bit >= 0; bit--) {
			if (((n >> bit) & 1) > 0) {
				sb.setCharAt(bit, '1');
			}
		}
		return sb.toString();
	}

	public static void main(String[] args) {
		try {
			VerticaBinaryFormatBitSet vbs = new VerticaBinaryFormatBitSet(Integer.valueOf(args[0]));
			for (int i = 1; i < args.length; i++) {
				vbs.setBit(Integer.valueOf(args[i]));
			}
			System.out.println("Little Endian Bit String Representation: " + vbs.toLittleEndianBinaryString());
		} catch (NumberFormatException e) {
			System.err.println("Usage: VerticaBinaryFormatBitSet <num bits> [bit index to set]...");
			e.printStackTrace();
		}
	}
}