What Is List Data Structure in Java?

Java is a versatile programming language that offers a wide range of data structures to efficiently store and manipulate data. One such fundamental data structure in Java is the List. A List is an ordered collection of elements that can contain duplicate values.

The List interface in Java is a part of the Java Collections Framework, which provides a set of classes and interfaces to handle collections of objects. It extends the Collection interface and defines behavior for adding, removing, and accessing elements in a specific order.

To use the List data structure in Java, you need to import the java.util.List package. Here’s how you can create a new instance of a List:


import java.List;
import java.ArrayList;

List names = new ArrayList<>();


In this example, we imported both the List and ArrayList classes from the java.util package. We created a new instance of the List, specifically an ArrayList, which is one implementation of the List interface.

Now, let’s explore some commonly used methods provided by the List interface:

Add Elements to List:

To add elements to a list, you can use the following methods:

• add(E element): Adds an element to the end of the list.

Example:

names.add("John");


This adds “John” to the end of our list.

—

• add(int index, E element): Adds an element at a specific position in the list.add(0, “Alice”);
  

  This adds “Alice” at the beginning of our list, shifting all other elements to the right.

Accessing Elements in List:

To access elements in a list, you can use the following methods:

• get(int index): Returns the element at the specified index.

Example:

String firstName = names.get(0);


This retrieves the first name from our list.

—

• size(): Returns the number of elements in the list.

Example:

int size = names.size();


This tells us how many names are currently stored in our list.

Removing Elements from List:

To remove elements from a list, you can use the following methods:

• remove(int index): Removes and returns the element at the specified index.

Example:

String removedName = names.remove(0);


This removes and returns the first name from our list.

—

• remove(Object element): Removes an occurrence of the specified element from the list.

Example:

boolean removed = names.remove("John");


This removes an occurrence of “John” from our list, if present.

List Iteration:

You can iterate over a list using various looping constructs like for-each or for loop. Here’s an example using the for-each loop:


for (String name : names) {
System.out.println(name);
}


This will print all the names in our list.

Conclusion:

In summary, the List data structure in Java provides an ordered collection of elements. It allows you to add, access, and remove elements efficiently.

By understanding and utilizing the methods offered by the List interface, you can effectively manage and manipulate your data in Java programs.