title: What is PECS (Producer Extends Consumer Super)?
body: <p>I came across PECS (short for <em>Producer <code>extends</code> and Consumer <code>super</code></em>) while reading up on generics. </p>
  
  <p>Can someone explain to me how to use PECS to resolve confusion between <code>extends</code> and <code>super</code>?</p>