Linked Lists in java

Let's start exploring linked lists. A linked list is a type of data structure. It's a series of connected objects, but it doesn’t involve arrays.
In a linked list, each element is connected to another because each element includes a reference to the next one.
This is different from arrays and array-based lists. In an array, each element doesn't know about the others, but in a linked list, each element knows the next one in sequence, requiring additional information to be stored with each element.

With an array of integers, we only store the integer values, but with a linked list, we store both the integer value and a reference to the next integer.

• For our implementation, we'll use an Employee class.
• Each element in a linked list is known as a node.
• The first element is called the head, and the last node points to null, indicating the end of the list.
• We'll create a Node class with a field for the data held in the node, in this case, an Employee field.
• Additionally, there will be a next field which is of type Node, as each node points to the next one.

This structure is known as a singly linked list since each node links to the next one only.

public class Employee {
   private String name;
   private String address;
   public Employee(String name, String address) {
       this.name = name;
       this.address = address;
   }
   @Override
   public String toString() {
       return "Employee{" +
               "name='" + name + '\'' +
               ", address='" + address + '\'' +
               '}';
   }
}

public class EmployeeNode {
    private Employee employee;
    private EmployeeNode next;
    public EmployeeNode(Employee employee) {
        this.employee = employee;
    }
    public EmployeeNode getNext() {
        return next;
    }
    public void setNext(EmployeeNode next) {
        this.next = next;
    }
    @Override
    public String toString() {
        return employee.toString();
    }
}

public class EmployeeLinkedList {
    private EmployeeNode head;
    private int size;
    public void addToFirst(Employee employee) {
        EmployeeNode node = new EmployeeNode(employee);
        node.setNext(head);
        head = node;
        size++;
    }
    public void printList() {
        EmployeeNode current = head;
        while (current != null) {
            System.out.println(current.toString());
            current = current.getNext();
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Employee e1 = new Employee("Kamal", "Balangoda");
        Employee e2 = new Employee("Bimal", "Ratnapura");
        Employee e3 = new Employee("Sumal", "Colombo");
        EmployeeLinkedList employeeLinkedList = new EmployeeLinkedList();
        employeeLinkedList.addToFirst(e1);
        employeeLinkedList.addToFirst(e2);
        employeeLinkedList.addToFirst(e3);
        employeeLinkedList.printList();
    }
}

Console output

    Employee{name='Sumal', address='Colombo'}
    Employee{name='Bimal', address='Ratnapura'}
    Employee{name='Kamal', address='Balangoda'}
    Process finished with exit code 0

The LinkedList class in Java

In Java, we don't need to manually implement a linked list because a linked list class is already provided.