ArrayList

#The Big Takeaway of this Unit

** ArrayLists: We can use ArrayLists to store data, and algorithms can be used to access and traverse through this data.**

#Exam Weighting

• 2.5-7.5% of the test
• Roughly 1 to 2 multiple-choice questions
• A possible topic of FRQ #3, which may test your ability to make ArrayLists and ArrayList algorithms.

#Enduring Understanding

We will now move on to the next data structure in this course, the ArrayList. Unlike the array, ArrayLists don't have a fixed size, and we can add and remove items from them. ArrayLists are part of the Java Collections Framework, which contains different data structures for different purposes. If you decide to learn more about Java in a second course, you will learn all about these data structures!

#Building Computational Thinking

ArrayLists are more versatile than arrays in many situations, but there are different methods that must be used to achieve this. Thus, it is important to know the difference between arrays and ArrayLists. Using ArrayLists, we will also learn how to sort and search elements, which are two of the most important applications.

#Main Ideas for this Unit 💡

• Creating ArrayLists
• ArrayList Methods
• Traversing ArrayLists
• ArrayList Algorithms
• Searching- Sequential/Linear Search
• Sorting- Selection Sort- Insertion Sort

#7.1 Introduction to ArrayList

An ArrayList is a data structure that allows you to store a collection of items in an ordered list. It is similar to an array, but it is dynamic in size, which means you can add or remove items from the list without having to specify the size of the list beforehand.

One of the key features of an ArrayList is its mutability. This means that the elements in the list can be changed after the list is created. For example, you can add or remove elements from the list, or you can change the value of an element at a specific index in the list.

To create an ArrayList, you can use the ArrayList constructor, which takes no arguments:

ArrayList list = new ArrayList<>();

You can also create an ArrayList with a specific initial capacity:

ArrayList list = new ArrayList<>(int initialCapacity);

The generic type E specifies the type of elements that will be stored in the ArrayList. For example, if you want to create an ArrayList that holds integers, you would use the type Integer like this:

ArrayList list = new ArrayList<>();

It is important to note that ArrayLists can only store objects, not primitive types (int, boolean, double). This is where the wrapper classes you learned about in Unit 2 come in! In order to add a primitive type to an ArrayList, you must first wrap the primitive type in its wrapper class to turn it into an object.

#7.2 ArrayList Methods

The ArrayList class is not part of the standard Java package, so it must be imported into your class so you can use it. This is the import statement you need to write...