Multiple choice technology programming languages

Click the Exhibit button. 10. interface Foo { 11. int bar(); 12. } 13. 14. public class Beta { 15. 16. class A implements Foo { 17. public int bar() { return 1; } 18. } 19. 20. public int fubar( Foo foo) { return foo.bar(); } 21. 22. public void testFoo() { 23. 24. class A implements Foo { 25. public int bar() { return 2; } 26. } 27. 28. System.out.println( fubar( new A())); 29. } 30. 31. public static void main( String[] argv) { 32. new Beta().testFoo(); 33. } 34. } Which three statements are true? (Choose three.)

  1. The code compiles and the output is 2

  2. If lines 16, 17 and 18 were removed, the code would compile and

  3. If lines 24, 25 and 26 were removed, the code would compile and the output would be 1

  4. D. If lines 24, 25 and 26 were removed, compilation would fail
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

The code compiles and outputs 2 because the local class A inside testFoo (lines 24-26) shadows the class A at lines 16-18. When fubar(new A()) is called, it uses the local A which returns 2. Removing lines 16-18 doesn't break compilation because the local A inside testFoo still implements Foo and satisfies the interface requirement. Removing lines 24-26 would cause fubar(new A()) to fail because A would no longer be defined in testFoo's scope - it would need to be Beta.A.

AI explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) The code compiles and the output is 2 - This option is incorrect. If lines 16, 17, and 18 were removed, the class A would not implement the bar() method from the Foo interface. Therefore, the code would not compile, and there would be no output.

Option B) If lines 16, 17, and 18 were removed, the code would compile and - This option is correct. If lines 16, 17, and 18 were removed, the class A would not implement the bar() method from the Foo interface. However, since the fubar() method accepts a parameter of type Foo, it can still accept an instance of any class that implements the Foo interface, including the nested class A defined in the testFoo() method. Therefore, the code would compile.

Option C) If lines 24, 25, and 26 were removed, the code would compile and the output would be 1 - This option is correct. If lines 24, 25, and 26 were removed, the nested class A defined in the testFoo() method would not be used. Instead, the class A defined outside the testFoo() method would be used, which implements the bar() method and returns 2. Therefore, the code would compile, and the output would be 2.

Option D) If lines 24, 25, and 26 were removed, compilation would fail - This option is incorrect. If lines 24, 25, and 26 were removed, the nested class A defined in the testFoo() method would not be used. However, the code would still compile and execute using the class A defined outside the testFoo() method.

Therefore, the correct answer is:

A) The code compiles and the output is 2 B) If lines 16, 17, and 18 were removed, the code would compile and C) If lines 24, 25, and 26 were removed, the code would compile and the output would be 1

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