TreeSet of partially ordered elements
<p>Java doc <code>TreeSet</code> contains enigmatic assertion: "<em>The behavior of a <code>TreeSet</code> is well-defined even if its ordering is strictly <strong>partial</strong>; it just fails to obey the general contract of the Set interface.</em> " I wonder how is it possible to supply partially ordered elements when <code>Comparable.compareTo()</code> is defined for any pair of elements and therefore implies <strong>total</strong> relation (if total relation is reflexive, antisymmetric, and transitive, then it's total order). </p>
