List Interface

June 26, 2025

📋 What is the `List` Interface?

The List interface in Java is a subinterface of Collection that represents an ordered collection of elements. It allows:

🧠 Package: java.util.List

Implementation	Characteristics
`ArrayList`	Fast for read, slow for insert/delete
`LinkedList`	Fast for insert/delete, slower for read
`Vector`	Synchronized (thread-safe, legacy)
`Stack`	LIFO (Last In First Out) structure

Method	Description
`add(E e)`	Adds an element at the end
`add(int index, E)`	Adds an element at specified index
`get(int index)`	Returns the element at given index
`remove(int index)`	Removes element at specified index
`set(int index, E)`	Updates element at index
`indexOf(Object o)`	Returns first index of element (or -1)
`size()`	Returns number of elements

import java.util.*;

public class ListExample {
public static void main(String[] args) {
List<String> cities = new ArrayList<>();

cities.add("Delhi");
cities.add("Mumbai");
cities.add("Chennai");
cities.add("Delhi"); // Duplicates allowed

cities.set(1, "Bangalore"); // Replace Mumbai with Bangalore

for (String city : cities) {
System.out.println(city);
}

System.out.println("City at index 0: " + cities.get(0));
}
}

Feature	`List` Interface
Order	Maintains insertion order
Duplicates	Allowed
Access	By index (zero-based)
Use cases	To-do lists, shopping carts, etc.