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public class BitString implements Cloneable {	private byte[] string;	private int length;		/**	 * Creates a new BitString filled with the length bits from data.	 * 	 * @param data input data	 * @param length the length of the new BitString	 */	public BitString(byte[] data, int length) {		if(length < 1)			throw new IllegalArgumentException("length must be bigger than 0");		if(data == null)			throw new IllegalArgumentException("data may not be null");		if((length - 1)/ 8 + 1 > data.length)			throw new IllegalArgumentException("data contains not enough elements for length: " + length);				string = new byte[(length - 1)/ 8 + 1];		for(int i = 0; i < string.length - 1; i++) string[i] = data[i];		this.length = length;		//set unused bits in last byte to zero!		if(length % 8 == 0) {			//no unused bits			string[string.length - 1] = data[string.length - 1];		} else {			//apply bitmask			byte mask = (byte) (255 << (8 - length % 8));			string[string.length - 1] = (byte) (data[string.length - 1] & mask);		}	}		/**	 * Creates an empty BitString	 */	public BitString() {		this.length = 0;	}		/**	 * Append a bit to the BitString	 * 	 * @param the bit to append to string	 * @return returns the complete BitString (this)	 */	public BitString append(boolean bit) {		if(this.length % 8 == 0) {			this.grow(1);		}		if(bit) {			//set bit			string[length / 8] = (byte) (string[length / 8] | (1 << (7 - length % 8)));		}		length++;		return this;	}		/**	 * Clones the BitString	 * 	 * @see java.lang.Object#clone()	 */	public BitString clone() {		return string == null ? new BitString() : new BitString(string.clone(), length);	}	/**	 * Returns the BitString as byte array	 * 	 * @return byte array or null if no bits are in BitString	 */	public byte[] getByteArray() {		return (this.string == null) ? null : this.string.clone();			}		/**	 * Returns the BitString as an boolean array	 * 	 * @return boolean array or null if no bits are in BitString	 */	public boolean[] getBitArray() {		//return "empty array"		if(this.length == 0) return null;				//build array		boolean[] result = new boolean[this.length];		int bitShift = 7;		int arrayPos = 0;		int resultPos = 0;		for (int i = 0; i < this.length; i++) {			result[resultPos++] = (string[arrayPos] & 1 << bitShift) != 0;			if(--bitShift < 0) {				bitShift = 7;				arrayPos++;			}		}		return result;	}		/**	 * Returns the cirrent length of the BitString (in bits)	 * 	 * @return the length of the BitString in bits	 */	public int getLength() {		return this.length;	}	/**	 * Allocates more space for bits	 * 	 * @param size	 */	private void grow(int size) {		if(this.string == null) {			this.string = new byte[size];		} else {			//create new array			byte[] newString = new byte[this.string.length + size];			//copy old content			for(int i = 0; i < this.string.length; i++) newString[i] = this.string[i];			//replace array			this.string = newString;		}	}	/**	 * Returns a '0', '1' string 	 * 	 * @see java.lang.Object#toString()	 */	public String toString() {		StringBuffer buffer = new StringBuffer();		int bitShift = 7;		int arrayPos = 0;		for (int i = 0; i < this.length; i++) {			buffer.append((string[arrayPos] & 1 << bitShift) != 0 ? "1" : "0");			if(--bitShift < 0) {				bitShift = 7;				arrayPos++;			}		}		return buffer.toString();	}}