Lists

**Lists** are a commonly used data structure in Java that allow you to store collections of data. Unlike Arrays, which have a fixed size, Lists can grow or shrink dynamically as elements are added or removed. In Java, the most commonly used implementation of a List is the **ArrayList** class, which is part of the `java.util` package. **Vocabulary terms to know for Lists:** - - **List**: An ordered collection of elements that can be accessed by their index. - **ArrayList**: A class in Java that implements the List interface using an Array to store the elements. - **LinkedList**: A class in Java that implements the List interface using a Linked List to store the elements. - **Element**: An individual item in a List. - **Index**: A numeric value that represents the position of an element in a List. - **Size**: The number of elements in a List. - **Iterator**: An object that provides a way to traverse the elements of a List. **Methods to know for Lists:** - - **`add()`**: A method used to add an element to a List. - **`clear()`**: A method used to remove all elements from a List. - **`contains()`**: returns `true` if the List contains the specified element, otherwise `false`. - **`get()`**: A method used to retrieve an element from a List at a specified index. - **`indexOf()`**: A method used to retrieve the index of a specified element in a List. - **`isEmpty()`**: A method used to check if a List is empty. - **`remove()`**: A method used to remove an element from a List. - **`set()`**: A method used to replace an element in a List at a specified index. - **`size()`**: returns the number of elements in the List. - **`subList()`**: A method used to retrieve a portion of a List between two specified indexes. To use an ArrayList, you first need to import the `java.util` package at the beginning of your code. Then, you can declare a new ArrayList variable and specify the type of data that the list will store. For example, to create an ArrayList that stores integers, you can do: import java.util.*; public class App { public static void main(String[] args) { ArrayList numbers = new ArrayList(); numbers.add(1); numbers.add(2); numbers.add(3); System.out.println(numbers.get(0)); } }

Java Week 4 - Lists