Introduction

• List is the child interface of the Collection interface.
• It is present in the java.util package.
• It was introduced in JDK 1.2 version.

• Hierarchy of List Interface:
  • 

• List is an ordered collection (also known as a sequence) and thus its elements can be accessed using index positions (like arrays).

• Syntax :-

  package java.util;
  
  public interface List extends Collection
  {
      // Methods (abstract)
  }

Methods of List Interface:

• Below are the methods defined specifically in the List interface:

Program :

• In below program, we are using List implemented class i.e. ArrayList.

• import java.util.ArrayList;
  import java.util.List;
  
  public class ListDemo
  {
      public static void main(String[] args)
      {
          List list = new ArrayList<>();
  
          // Adding elements
          list.add("Java");
          list.add("Python");
          list.add("C++");
          list.add("Java"); // duplicate allowed
  
          // Accessing elements
          System.out.println("Element at index 1: " + list.get(1));
  
          System.out.println("-------------------------");
  
          // Updating element
          list.set(2, "C#");
          System.out.println(list);
  
          System.out.println("-------------------------");
  
          // Removing element
          list.remove(0);
          System.out.println(list);
  
          System.out.println("-------------------------");
  
          // Iterating list
          for(String lang : list)
          {
              System.out.println(lang);
          }
      }
  }

  Output:

  Element at index 1: Python
  -------------------------
  [Java, Python, C#, Java]
  -------------------------
  [Python, C#, Java]
  -------------------------
  Python
  C#
  Java

Properties of List Interface:

1. List is an index-based data structure; the first element is stored at index 0.
2. List can store heterogeneous elements if used without generics, but with generics it stores only homogeneous elements of the specified type.
3. List allows duplicate elements.
4. List can store null values.
5. List maintains insertion order, meaning elements are retrieved in the same order they are inserted.
6. List does not sort elements automatically; sorting must be done explicitly using Collections.sort() or list.sort().