URGENT Array List Question

[iWaterBuffalo]

Suppose that you have an ArrayList and that it contains String objects.
Which declaration of the ArrayList requires that objects retrieved using the
get method be cast to Strings before calling a String method?

I. ArrayList a = new ArrayList();
II. ArrayList<Object> a = new ArrayList<Object>;
III. ArrayList<String> a = new ArrayList<String>;

A. I only
B. II only
C. III only
D. I and II only
E. I, II, and III


I really have no idea on this question. I know that all of these are ways to declare an Array List, but I am unfamiliar with the last two since I usually just declare my Array Lists with the first option.

[copeg]

Recommended reading: Lesson: Generics (Updated) (The Java™ Tutorials > Learning the Java Language)

[iWaterBuffalo]

Okay, so I know that I is definitely correct. So that brings me down to A or D. Would <Object> behave the same as <String>?

[GregBrannon]

Your last question is a good one. If the answer is not obvious after about 15 seconds of thought, you could write a simple program to see if calling a String method with an Object is the same as calling a String method with a String instance.

[iWaterBuffalo]

Thank you both. I figured out the correct answer.

[PitLv]

Only III is correct. Even though you may use I & II to create a String ArrayList, you still need to cast them before using.

[copeg]

Only III is correct. Even though you may use I & II to create a String ArrayList, you still need to cast them before using.

Is that your final answer?

Which declaration of the ArrayList requires that objects retrieved using the
get method be cast to Strings before calling a String method?