What happens when you try to add a primitive type to an ArrayList?

• A. It throws a compilation error
• B. It is automatically converted into its corresponding wrapper class
• C. It adds the value directly without conversion
• D. It is not allowed and results in a runtime exception

Answer: (B)

When you attempt to add a primitive type to an ArrayList, it is automatically converted into its corresponding wrapper class. This process, known as boxing, enables the ArrayList to store the value because ArrayLists in Java can only hold objects, while primitive types (such as int, char, double, etc.) are not objects.

For example, if you add an integer (a primitive type) to an ArrayList, Java automatically wraps it into an Integer object, which is the corresponding wrapper class for the int primitive type. This automatic conversion ensures that you can store values in an ArrayList without needing to manually convert each primitive to its object form before adding it to the list.

If you tried to add a primitive directly without this conversion, it would result in a compilation error because the types would not match; however, due to Java's built-in mechanism for autoboxing, this conversion happens seamlessly. Thus, the correct choice highlights the fundamental behavior of how Java manages primitive types and their corresponding wrapper classes within collections like ArrayList.