title: Class design if two class needs to exchange information
body: <p>If I have two classes as</p>
  
  <pre><code>class A
  {
  }
  </code></pre>
  
  <p>and </p>
  
  <pre><code>class B
  {
  }
  </code></pre>
  
  <p><code>class A</code> wants to use methods of <code>class B</code> and vice-versa.</p>
  
  <p>What should be the best design other than the mediator pattern?</p>