title: solid line arrow vs dotted line arrow in class hierarchy diagram
body: <p>I'm currently learning java collection. I have been shown a class hierarchy diagram of <code>Set</code> interface and its sub-interfaces and concrete implementation classes. </p>
  
  <p><a href="https://i.stack.imgur.com/lho5A.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lho5A.png" alt="enter image description here"></a></p>
  
  <p>No explanation was provided for the meaning of solid line arrow and dotted line arrow. </p>
  
  <p>Using my own judgement, I assumed that solid line arrow means <strong>extends</strong>, and dotted line arrow means <strong>implements</strong>, but is my assumption correct? </p>
  
  <p>Is there any official documentation for meaning and usage of such symbols? </p>