Question

Analyze the following code:

ArrayList list = new ArrayList();
list.add("Beijing");
list.add("Tokyo");
list.add("Shanghai");
list.add(3, "Hong Kong");


A. The last line in the code causes a runtime error because there is no element at index 3 in the array list.
B. The last line in the code has a compile error because there is no element at index 3 in the array list.
C. If you replace the last line by list.add(3, "Hong Kong"), the code will compile and run fine.
D. If you replace the last line by list.add(4, "Hong Kong"), the code will compile and run fine.

Answer 1

Option C is correct. Using 'list.add(3, "Hong Kong")' correctly inserts 'Hong Kong' at index 3 in the ArrayList without causing errors, as it is the next available index after adding three elements.

Step-by-step explanation:

Analyzing the given code snippet with an ArrayList, various scenarios can be discussed regarding the indexing and insertion of elements:

• Option A mentions a runtime error for adding an element at index 3. This is incorrect because index 3 is valid as it would come after the third element is added to the list.
• Option B speaks of a compile error for the same reason, which is also incorrect due to the same rationale as in Option A.
• Option C claims that using list.add(3, "Hong Kong") will compile and run fine, and this statement is true. After adding three cities, index 3 is the next valid index for a new element.
• Option D suggests using index 4, but this would cause a runtime error since there are not yet five elements in the list (indices start at 0).

Therefore, the correct answer to the original question is C: replacing the last line with list.add(3, "Hong Kong") will allow the code to compile and run without errors.