public class AB3
{
    public boolean valsLess(TreeNode t, Comparable obj)
    {
	if (t == null) return true;

	Comparable c = (Comparable) t.getValue();
	return c.compareTo(obj) < 0 &&
	    valsLess(t.getLeft(),obj) &&
	    valsLess(t.getRight(), obj);
    }
    
    public boolean valsGreater(TreeNode t, Comparable obj)
    {
	if (t == null) return true;

	Comparable c = (Comparable) t.getValue();
	return c.compareTo(obj) > 0 &&
	    valsGreater(t.getLeft(),obj) &&
	    valsGreater(t.getRight(), obj);
    }
    
    public boolean isBST(TreeNode t)
    {
	if (t == null) return true;

	Comparable c = (Comparable) t.getValue();
	return
	    valsLess(t.getLeft(), c) &&
	    valsGreater(t.getRight(), c) &&
	    isBST(t.getLeft()) &&
	    isBST(t.getRight());
    }
}