This tutorial will show you a Linked List implementation in Java. It will have following features-
- Add nodes from both ends (Beginning and End)
- Delete nodes from Beginning
- Get count of nodes
- Get First & Last node
- Get Node at a specific position
Please let me know if you find some incorrect scenarios.
Node structure-
/**
* LinkedList Node
*/
public class Node {
/**
* Holds any type of Object Data
*/
public Object data;
/**
* Pointer to a Node
*/
public Node pointer;
}
Linked List
/**
* LinkedList Implementation
*/
public class LinkedList {
Node first;
/**
* Stores the count of nodes in the linked list
*/
int count;
/**
* Add an element at the beginning
* @param data
*/
public void addToBeginig(Object data){
if(first == null){
/*
* The Linkedlist is empty and adding the first node
*
*/
Node node = new Node();
node.data = data;
node.pointer = null;
first = node;
count = 1;
return;
}
// Add the node at the beginning
Node newFirst = new Node();
newFirst.data = data;
newFirst.pointer = first;
first = newFirst;
count++;
}
/**
* Add one element at the end of the list
* You can store multiple type Objects in a single LinkedList
* e.g. String, your Custom Class etc. as long as you cast it properly
* @param data
*/
public void addToEnd(Object data){
if(first == null){
/*
* The Linkedlist is empty and adding the first node
*
*/
Node node = new Node();
node.data = data;
node.pointer = null;
first = node;
count = 1;
return;
}
Node next = first;
while(next.pointer != null){
next = (Node)next.pointer;
}
// Add the node at the end
Node newNode = new Node();
newNode.data = data;
newNode.pointer = null;
next.pointer = newNode;
count++;
}
/**
* Deletes the first node
*/
public void deleteFromBegining(){
if(first == null){
/*
* The Linklist is empty, nothing to delete
*/
count = 0;
return;
}
// get the pointer to next node
Node next = first;
// delete the first node
first = null;
// make the next node as first node
first = next.pointer;
count--;
}
/**
* Get the first node
* @return
*/
public Node getFirst(){
return first;
}
/**
* Get the last node
* @return
*/
public Node getLast(){
Node next = first;
while(next.pointer != null)
next = next.pointer;
return next;
}
/**
* Get a node at a particular position
* @param nodeID
*/
public Object get(int position){
/*
* If the position index is more than the count of
* nodes in the Linkedlist, throw Exception
*/
if(position >= count)
throw new IndexOutOfBoundsException();
Node next = first;
int i = 0;
if(i == position)
return next.data;
while(next.pointer != null){
next = next.pointer;
i++;
if(i == position)
return next.data;
}
// for the last element
i++;
return next.data;
}
/**
* Returns the count of nodes stored in LinkedIn
* @return
*/
public int count(){
return count;
}
}
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