// AI

        public void setTree(Tree tree) {
        this.tree = tree;
    }

    private void chopTrees() throws SuspendExecution {
        while (started) {
            Tree tree = (this.tree != null ? this.tree : unit.getWorld().getNearestTree(new Point(unit.getX(),unit.getY())));
            if (tree == null) {
                unit.stopChopping();
                return;
            }

            moveTo(tree.getPosition());

            if (!chop(tree))
                continue;

            WoodStorage storage = unit.getWorld().getNearestWoodStorage(unit.getPosition());
            Point p1 = storage.getDeliveryPoint();
            Point p2 = storage.getPosition();
            p2.translate(p1.x,p1.y);
            moveTo(p2);

            storeInto(storage);

            if (this.tree != null) {
                this.tree = null;
                unit.stopChopping();
            }
        }
    }


// Unit

public void startChopping() {
        unitAI.startAI();
    }

    public void stopChopping() {
        unitAI.stopAI();
    }

    public void chop(Tree tree) {
        unitAI.setTree(tree);
        startChopping();
    }