Introduction to Linked Lists

A linked list is a data structure used for storing collections of data. A linked list has the following properties:

• Successive elements are connected by pointers.
• The last element points to null.
• Can grow or shrink in size during execution of a program.
• Can be made just as long as required (until system memory exhausts).
• Does not waste memory space (but takes some extra memory for storing pointers). It allocates memory as list grows.

Linked Lists are comprises of Nodes.

What is a Node?

A Node in a Linked List is a fundamental building block that holds two pieces of information:

1. data – the actual value or information you want to store (like an integer, string, object, etc.).
2. next (Pointer or Reference) – a link to the next node in the list.

How do we represent a Node in Java?

class Node {
    int data;
    Node next;

    Node(int data) {
        this.data = data;
    }
}

Create a linked list using nodes

Step 1: Create individual nodes

Node node1 = new Node(123);
Node node2 = new Node(321);

Step 2: Link the first node to the second

node1.next = node2;

Step 3: Access linked nodes

System.out.println(node1.data);         // 123
System.out.println(node2.data);         // 321
System.out.println(node1.next.data);    // 321

Complete Java Code

Create a class BasicNodeStructure.java.

class Node {
    int data;
    Node next;

    Node(int data) {
        this.data = data;
    }
}

public class BasicNodeStructure {
    public static void main(String[] args) {
        Node node1 = new Node(123);
        Node node2 = new Node(321);
        node1.next = node2;
        System.out.println(node1.data);
        System.out.println(node2.data);
        System.out.println(node1.next.data);
    }
}

Compile and run by running following two commands.

javac BasicNodeStructure.java

java BasicNodeStructure

Output

123
321
321