the useful subclass for BitSet and FastBitSet

BitSet and FastBit will always change themselves if they do some set operations, just like and, or, andNot. To avoid such cases, you should write a extended classes:

For BitSet: MyBitSet

import java.util.BitSet;

/**
 * @author Conny Gu This Class extends from Class BitSet, it won't change
 *         itself while it does some operations.
 * 
 */

public class MyBitSet extends BitSet {

	public MyBitSet() {
		super(0);
	}

	public MyBitSet(int nbits) {
		super(nbits);
	}

	/**
	 * This myand() funktion will return a BiSet and itself won't be changed.
	 * 
	 * @param b
	 * @return MyBitSet
	 */
	public MyBitSet myand(MyBitSet b) {
		MyBitSet a = (MyBitSet) this.clone();
		a.and(b);
		return a;
	}

	public MyBitSet myor(MyBitSet b) {
		MyBitSet a = (MyBitSet) this.clone();
		a.or(b);
		return a;
	}

	/**
	 * This myandNot() funktion will return a BiSet and itself won't be changed.
	 * 
	 * @param b
	 * @return MyBitSet
	 */

	public MyBitSet myandNot(MyBitSet b) {
		MyBitSet a = (MyBitSet) this.clone();
		a.andNot(b);
		return a;
	}

}

For FastBitSet: MyFastBitSet

import javolution.util.FastBitSet;

/**
 * @author Conny Gu This Class extends from Class FastBitSet, it won't change
 *         itself while it does some operations.
 * 
 */

public class MyFastBitSet extends FastBitSet {

	public MyFastBitSet() {
		super();
	}

	public MyFastBitSet(FastBitSet b) {
		super();
		this.addAll(b);

	}

	
	public MyFastBitSet myand(MyFastBitSet b) {

		MyFastBitSet a = new MyFastBitSet();

		a.addAll(this);

		a.and(b);

		return a;

	}

	public MyFastBitSet myor(MyFastBitSet b) {

		MyFastBitSet a = new MyFastBitSet();

		a.addAll(this);

		a.or(b);

		return a;

	}

	public MyFastBitSet myandNot(MyFastBitSet b) {

		MyFastBitSet a = new MyFastBitSet();

		a.addAll(this);

		a.andNot(b);

		return a;

	}

}