Java Singly Linked List Implementation

Here you will get program to implement singly linked list in Java.

Linked list is a linear data structure. It contains different nodes. Each node will store data and reference to the next node. This is the most useful data structure in computer science in construction of trees especially.

Java Singly Linked List Implementation

import java.util.*;

// we will create a node class first with data members
class Node
{
	int data;  
	// node class should be self referential because it has to refer the next node  
	Node next;
	
	//set data value, next node reference through method
	public Node(int d)
	{
		data=d;
		next=null;
	}
}

//Now we will create LinkedList class
class Linkedlist{
	Node head;
	
	//function to check whether linked list is empty or not
	public boolean isEmpty()
	{
		if(head==null)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	
	//function for inserting element in the begining
	public void insertionAtBegining(int val)
	{
		if(isEmpty())
		{
			head=new Node(val);
		    
		}
		else{
			Node temp=new Node(val);
			temp.next=head;
			head=temp;
			
		}
	}
	
	//function for inserting at end
	public void insertionAtEnd(int val)
	{
		if(isEmpty())
		{
			head=new Node(val);
		}
		else{
			Node temp=head;
			while(temp.next!=null)
			{
				temp=temp.next;
			}
			temp.next=new Node(val);
			
		}
	}
	
	//function for insertion at specified position
	public void insertionAtPos(int val, int pos)
	{
		int count=1;
		Node temp=head;
		while(temp!=null)
		{
			count++;
			if(count==pos)
			{   
		        Node post = temp.next;
				temp.next = new Node(val);
				temp.next.next = post;
				
			}
			
			temp = temp.next;
		}
		if(count < pos)
			{
				System.out.println(count);
				System.out.println("linked list is in underflow to insert at specified position");
			}
	}
	
	//function to traverse and print entire list
	public void printlist()
	{
		System.out.print("list is ");
		Node temp = head;
		while(temp != null)
		{
			System.out.print(" "+temp.data);
			temp=temp.next;
		}
		
	}
	
	//function to delete at first
	public void deleteAtBegining()
	{
		head = head.next;
		
	}
	
	// function to delete at specified postion
	public void deleteAtPos(int pos)
	{
		int count = 1;
		Node temp = head;
		while (temp != null)
		{
			count++;
			
			if(count == pos)
			{
				break;
			}
			temp=temp.next;
		}
		if(count < pos)
		{
			System.out.println("linked list is in underflow condition to delete in the position" +pos);
		}
	
		temp.next = temp.next.next;
	}
	
	// function to delete at end
	public void deleteAtEnd()
	{
		Node temp = head;
		while( temp.next.next != null )
		{
			temp = temp.next;
		}
		temp.next = null;
	}
	
	// function to search for an element in the linked list
	public void search(int val)
	{
		Node temp = head;
		int count = 0;
		int flag = 0;
		
		while(temp != null)
		{
			count++;
			if(temp.data == val)
			{
				System.out.println( val + " found at pos " + count );
				flag = 1;
			}
			
			temp = temp.next;
		}
		
		if(flag == 0)
		{
			System.out.println(val +" not found");
		}	 
	}
	
	public static void main(String args[])
	{
		Linkedlist listObj = new Linkedlist();  

		System.out.println("adding elements to linked list at begining:");
		listObj.insertionAtBegining(4);
		System.out.println("4 is added in linked list");
		listObj.printlist();
		listObj.insertionAtBegining(5);
		System.out.println("\n5 is added in linked list");
		listObj.printlist();
		listObj.insertionAtBegining(7);
		System.out.println("\n7 is added in linked list");
		listObj.printlist();
		listObj.insertionAtBegining(10);
		System.out.println("\n10 is added in linked list");
		listObj.printlist();
		
		System.out.println("\n\nadding elements to linked list at end:");
		listObj.insertionAtEnd(6);
		System.out.println("6 is added at the end of linked list");
		listObj.insertionAtEnd(20);
		System.out.println("20 is added at the end of linked list");
		listObj.insertionAtEnd(30);
		System.out.println("30 is added at the end of linked list");
		listObj.printlist();
	
		listObj.insertionAtPos(8,2);
		System.out.println("\n\n8 is added at the 2nd index of linked list");
		listObj.printlist(); 
		
		System.out.println("\n\ndeleted the first element");
		listObj.deleteAtBegining();
		listObj.printlist(); 
		
		listObj.deleteAtPos(2);
		System.out.println("\ndeleted the element at pos 2");
		listObj.printlist();
		listObj.deleteAtEnd();
		System.out.println("\ndeleted the element at end");
		listObj.printlist();
		
		System.out.println("\n\nsearching element 5 in list");
		listObj.search(8);
		System.out.println("\nsearching element 15 in list");
		listObj.search(15);
	}
}

Output

adding elements to linked list at begining:
4 is added in linked list
list is 4
5 is added in linked list
list is 5 4
7 is added in linked list
list is 7 5 4
10 is added in linked list
list is 10 7 5 4

adding elements to linked list at end:
6 is added at the end of linked list
20 is added at the end of linked list
30 is added at the end of linked list
list is 10 7 5 4 6 20 30

8 is added at the 2nd index of linked list
list is 10 8 7 5 4 6 20 30

deleted the first element
list is 8 7 5 4 6 20 30
deleted the element at pos 2
list is 8 5 4 6 20 30
deleted the element at end
list is 8 5 4 6 20

searching element 5 in list
8 found at pos 1

searching element 15 in list
15 not found

Comment below if you have any queries related to above java singly linked list program.