title: Real life generic class examples
body: <p>I got next question at Java interview:</p>
  
  <ol>
  <li><p>Could you name some generic class examples from real life? Not from real PROGRAMMING life, but in common. E.g. you are explaining generics to person, who doesn't know anything about programming.</p></li>
  <li><p>Same thing about the most easy design pattern - singleton.</p></li>
  </ol>
  
  <p>I have know any idea, about first question (about generics), I tried to name different hand tools (like fretsaw), which work with only one type of material, but it is not generics really.</p>
  
  <p>Please, avoid collection-like suggestions, it is too naive and obvious.</p>