Which class definition compiles?

Question

Options

• A

  class Vehicle {
   int id;
   public void start() {
   public class Engine { int eNo = id; }
   }
  }
  

• B

  class Computer {
   private Card sCard = new SoundCard();
   private abstract class Card { }
   private class SoundCard extends Card { }
  }
  

• C

  class Block {
   int bNo;
   static class Counter {
   int locator;
   Counter() { locator = bNo; }
   }
  }
  

• D

  class Product {
   interface Moveable { void move(); }
   Moveable mProduct = new Moveable() {
   void move() { }
   };
  }
  

• A
  10% (6)
• B
  71% (44)
• C
  16% (10)
• D
  3% (2)

Explanation

Option B compiles because it correctly uses a private abstract member class (Card) as a type, with a concrete private inner class (SoundCard) that extends it - all at the member level of the outer class, where access modifiers and inheritance are fully permitted.

Option A fails because local classes (defined inside a method body) cannot have access modifiers like public - that keyword is illegal in that context.

Option C fails because static nested classes have no reference to an outer instance, so bNo (an instance field of Block) is inaccessible from the static Counter class.

Option D fails because the anonymous class implements the Moveable interface but declares move() without the public modifier - interface methods are implicitly public, and you cannot reduce visibility when overriding, so the compiler rejects it.

Memory tip: Think "SPAM" - Static nested classes can't see instance fields, Public is required when implementing interface methods, Access modifiers are banned on local classes. If a choice violates any of these, it won't compile.

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