Multiple choice technology programming languages

Given: 11. public static Iterator reverse(List list) { 12. Collections.reverse(list); 13. return list.iterator(); 14. } 15. public static void main(String[] args) { 16. List list = new ArrayList(); 17. list.add(” 1”); list.add(”2”); list.add(”3”); 18. for (Object obj: reverse(list)) 19. System.out.print(obj + “,”); 20. } ‘What is the result?

  1. 3,2, 1,

  2. 1, 2, 3,

  3. Compilation fails.

  4. The code runs with no output.

  5. An exception is thrown at runtime.
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C Correct answer
Explanation

The reverse() method returns a raw Iterator (not Iterator). When used in the for-each loop, Java cannot determine the type parameter for the iterator. For-each loops require an array or a generic Iterable. Raw Iterator doesn't implement Iterable properly, so this fails to compile. The fix is to return Iterator.

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