OCPJP Simulation Test 4

4

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Question: What is the output of the following program?

  1 public abstract class Email {
  2   private String recipient;
  3   void sendEmail(){};
  4   public static void main(String args[]) {
  5     Email email = new XyzEmail();
  6     email.recipient = "John@xyznetwork.com";
  7     email.sendEmail();
  8   }
  9   static class XyzEmail extends Email {
 10     public final void sendEmail()  {
 11       System.out.println("Email is sent to " + recipient);
 12     }}}

Choice:
A. Email is sent to John@xyznetwork.com
B. Email is sent to
C. Email is sent to null
D. Compilation error at line 2
E. Compilation error at line 3
F. Compilation error at line 5
G. Compilation error at line 9
H. Compilation error at line 11



Next Question

Answer: H

Explain: The abstract class Email has a static nested class XyzEmail. Email doesn't have abstract method, it has a concrete method sendEmail, which is overrides by XyzEmail. As a static nested class of Email, XyzEmail can not access local variables of enclosing class, in this case the private variable recipient. If recipient have access modifiers default (no access modifier), protected or public, the answer will be A.

Study:  Develop code that uses abstract classes and methods

     Develop code that uses final keyword

     Create inner classes including static inner class, local class, nested class, and anonymous inner class