public static Tree balance(Tree a)
    {
    	if (a.getEmpty())
    	{
    		return a;
    	}
    	else if (a.getLeft().getEmpty() && a.getRight().getEmpty())
    	{
    		return a;
    	}

    	Tree leftSubTree = balance(a.getLeft());
    	Tree rightSubTree = balance(a.getRight());

    	Tree b = new Tree(a.getValue(), leftSubTree, rightSubTree);

    	if (b.getLeft().getHeight() - b.getRight().getHeight() == 0 || b.getLeft().getHeight() - b.getRight().getHeight() == 1)
    	{
    		return b;
    	}
    	else if (b.getLeft().getHeight() - b.getRight().getHeight() >= 2)
    	{
    		return rotateRight(b);
    	}
    	else
    	{
    		return rotateLeft(b);
    	}
    }