title: Composition vs Inheritance
body: <p>I have a <code>Validator</code> interface with one method signature: <code>public List&lt;ParameterError&gt; validateParameters(Parameters parameters);</code> Various classes implement this interface.</p>
  
  <p>There are also some common methods like <code>isInteger</code>, <code>isInRange</code>, etc. Should I have these methods in a <code>ValidationHelper</code> and use composition in the classes implementing the <code>Validator</code> interface, or should I make <code>Validator</code> an abstract class, put these methods there and use inheritance instead of composition?</p>