title: Accessing a randomly-assigned object
body: <p>Given the following:</p>
  
  <pre><code>class ClassA
  
  class ClassA1 extends ClassA
  class ClassA2 extends ClassA
  class ClassA3 extends ClassA
  
  ClassA1 a1 = new ClassA1()
  ClassA2 a2 = new ClassA2()
  ClassA3 a3 = new ClassA3()
  
  ClassA a = either a1, a2, or a3 (programmed to be randomly chosen by JVM)
  </code></pre>
  
  <p>If the reference to the subclass object (either 'a1', 'a2', or 'a3') is only assigned to the superclass reference variable 'a' at runtime, how can I write an 'if' statement that implements: if 'a' refers to a1, access a specified field of a1 (which is not inherited from a)? Any assistance on this would be appreciated.</p>