private GayBerneParticle whichParticleOtherThan(int x, int y, GayBerneParticle p) {
		Rectangle2D r2d = new Rectangle2D.Double();
		for (int i = 0; i < nParticle; i++) {
			if (gb[i] != p) {
				at.setToRotation(gb[i].getTheta(), gb[i].getRx(), gb[i].getRy());
				r2d.setRect(gb[i].getRx() - gb[i].getLength() * 0.5 - 3.0, gb[i].getRy() - gb[i].getBreadth() * 0.5 - 3.0, gb[i].getLength() + 6.0, gb[i].getBreadth() + 6.0);
				if (at.createTransformedShape(r2d).contains(x, y))
					return gb[i];
			}
		}
		return null;
	}