List

The List interface is a part of the Java Collections Framework and represents an ordered collection that can contain duplicate elements. Unlike Set, a List maintains the order in which elements are inserted and allows for random access to its elements via an index.

Key Implementations of List

  1. ArrayList:

    • An ArrayList is a resizable array implementation of the List interface. It provides fast random access to elements but can be slower when adding or removing elements at arbitrary positions (except at the end).
    List<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");


2. **LinkedList**:

   * A `LinkedList` is a doubly linked list implementation of the `List` interface. It offers better performance than `ArrayList` when adding or removing elements from the beginning or middle of the list.

   ```java
   List<String> names = new LinkedList<>();
   names.add("Alice");
   names.add("Bob");

  1. Vector:

    • A Vector is similar to an ArrayList, but it is synchronized, making it thread-safe. However, its usage has been largely replaced by ArrayList.
    List<String> names = new Vector<>();
names.add("Alice");
names.add("Bob");

Important Methods in List

  1. add(E e):

    • Adds the specified element to the list.
    list.add("Alice");

  2. get(int index):

    • Retrieves the element at the specified position in the list.
    String name = list.get(0); // Access first element

  3. remove(int index):

    • Removes the element at the specified position.
    list.remove(0); // Removes the first element

  4. set(int index, E element):

    • Replaces the element at the specified position with the specified element.
    list.set(0, "New Name");

  5. contains(Object o):

    • Checks if the list contains the specified element.
    boolean containsAlice = list.contains("Alice");

  6. size():

    • Returns the number of elements in the list.
    int size = list.size();

Example: Using List

import java.util.*;

public class ListExample {
    public static void main(String[] args) {
        // Creating a List
        List<String> names = new ArrayList<>();
        
        // Adding elements
        names.add("Alice");
        names.add("Bob");
        names.add("Charlie");
        
        // Retrieving an element
        System.out.println("First element: " + names.get(0)); // Output: Alice
        
        // Removing an element
        names.remove("Bob");
        
        // Checking size
        System.out.println("Size of list: " + names.size());
        
        // Iterating through the list
        for (String name : names) {
            System.out.println(name);
        }
    }
}

🔗 Related Notes