2.2 Lists Explained

Lists in Java are a fundamental part of the Java Collections Framework, providing a way to store and manipulate collections of objects. Understanding lists is crucial for managing ordered collections efficiently.

Key Concepts

1. List Interface

The List interface extends the Collection interface and represents an ordered collection of elements. It allows duplicate elements and provides methods to access elements by their index.

Example

        List list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Cherry");
        System.out.println(list.get(1)); // Output: Banana
    

2. ArrayList

An ArrayList is a resizable array implementation of the List interface. It provides fast random access and is suitable for scenarios where elements are frequently accessed by index.

Example

        List arrayList = new ArrayList<>();
        arrayList.add(10);
        arrayList.add(20);
        arrayList.add(30);
        System.out.println(arrayList.get(2)); // Output: 30
    

3. LinkedList

A LinkedList is a doubly-linked list implementation of the List interface. It provides efficient insertion and deletion operations but slower random access compared to ArrayList.

Example

        List linkedList = new LinkedList<>();
        linkedList.add("Dog");
        linkedList.add("Cat");
        linkedList.add("Bird");
        System.out.println(linkedList.get(1)); // Output: Cat
    

4. List Operations

Lists support various operations such as adding elements, removing elements, accessing elements by index, and iterating through the list.

Example

        List fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Cherry");
        
        fruits.remove("Banana");
        System.out.println(fruits); // Output: [Apple, Cherry]
        
        for (String fruit : fruits) {
            System.out.println(fruit);
        }
    

Examples and Analogies

Think of a List as a numbered list of items, similar to a shopping list where each item has a specific position. An ArrayList is like a dynamic array that can grow or shrink as needed, while a LinkedList is like a chain of items where each item is connected to the next and previous items.

By mastering lists, you can efficiently manage and manipulate ordered collections of data in your Java SE 11 applications.