Exploring ArrayLists in Java

What is an ArrayList?

• An ArrayList is a resizable array implementation of the List interface in Java.

• An ArrayList is a fixed-size array in Java.

• An ArrayList is a type of linked list in Java.

• An ArrayList is a collection of primitive data types in Java.

Answer explanation

An ArrayList is a resizable array implementation of the List interface in Java, allowing dynamic size changes. The other options incorrectly describe it as fixed-size, a linked list, or a collection of primitives.

How does an ArrayList differ from a regular array?

• An ArrayList is always faster than a regular array.

• An ArrayList requires manual memory management unlike a regular array.

• A regular array can store more data types than an ArrayList.

• An ArrayList can dynamically resize and provides built-in methods for manipulation, while a regular array has a fixed size and lacks such methods.

Answer explanation

An ArrayList can dynamically resize and offers built-in methods for adding, removing, and manipulating elements, unlike a regular array, which has a fixed size and lacks these functionalities.

What method would you use to add an element to an ArrayList?

• Use the 'push' method.

• Use the 'insert' method.

• Use the 'append' method.

• Use the 'add' method.

Answer explanation

To add an element to an ArrayList in Java, you use the 'add' method. The other options like 'push', 'insert', and 'append' are not valid methods for ArrayList, making 'add' the correct choice.

How can you access the first element of an ArrayList?

• arrayList[0]

• arrayList.getFirst()

• arrayList.get(0)

• arrayList.first()

Answer explanation

To access the first element of an ArrayList in Java, you should use the method arrayList.get(0). The other options are incorrect as they either use invalid syntax or non-existent methods.

What method would you use to remove an element from an ArrayList?

• Use the remove() method.

• Use the pop() method.

• Use the clear() method.

• Use the delete() method.

Answer explanation

The correct method to remove an element from an ArrayList is the remove() method. The pop() method is not applicable, clear() removes all elements, and delete() is not a valid method for ArrayLists.

How do you iterate through an ArrayList using a for-each loop?

• for (Type element : arrayList.iterator()) { // process element }

• for (Type element : array) { // process element }

• for (Type element : arrayList) { // process element }

• for (int i = 0; i < arrayList.size(); i++) { // process arrayList.get(i) }

Answer explanation

The correct choice is 'for (Type element : arrayList) { // process element }' because it directly iterates through each element in the ArrayList, allowing for easy access to each item without needing an index.

What method can you use to clear all elements from an ArrayList?

• Use the clear() method.

• Invoke the delete() method.

• Use the removeAll() method.

• Call the reset() method.

Answer explanation

The clear() method is specifically designed to remove all elements from an ArrayList, making it the correct choice. The other options, such as delete(), removeAll(), and reset(), do not serve this purpose.

How can you check the size of an ArrayList?

• Check arrayList.count() for the size of an ArrayList.

• Call arrayList.getSize() to find the size of an ArrayList.

• Use arrayList.length() to check the size of an ArrayList.

• Use arrayList.size() to check the size of an ArrayList.

Answer explanation

The correct way to check the size of an ArrayList in Java is by using arrayList.size(). The other options, such as count(), getSize(), and length(), are not valid methods for ArrayList.

What is the purpose of Collections.sort() in relation to an ArrayList?

• To sort the elements of an ArrayList in ascending order.

• To remove duplicate elements from an ArrayList.

• To reverse the order of elements in an ArrayList.

• To filter elements of an ArrayList based on a condition.

Answer explanation

Collections.sort() is used to arrange the elements of an ArrayList in ascending order. This is the primary function of the method, making the first answer choice correct.

How can you check if an ArrayList contains a specific element?

• Use arrayList.get(index) to find the element;

• Use arrayList.contains(element);

• Use arrayList.has(element);

• Check if element is in arrayList.size();

Answer explanation

To check if an ArrayList contains a specific element, use arrayList.contains(element);. This method returns true if the element is found, making it the correct choice. The other options do not effectively check for element presence.