In this article, we will discuss LinkedList class – one of the List implemented class in detail

1. LinkedList:

• LinkedList is implementation class of List interface (i.e.; LinkedList implements List)
• LinkedList uses doubly-linked list to store element/objects
• Duplicate element/objects are allowed to be inserted into LinkedList
• Insertion order is maintained
• Allows NULL insertion (no limit, we can insert any number of NULL to LinkedList)
• Without generics, LinkedList allows to insert any type of objects;
• With generics, it is type-bounded (except, if we take Object as type within angle brackets)
• Manipulation (i.e.; addition/deletion/updation of element from middle of LinkedList) is very fast, as it works on the basis of previous & next nodes and there is no shifting required
• Elements retrieval is much slower, as LinkedList need to iterate over complete list to retrieve/get the required item/element
• LinkedList is non-synchronized
• Present in java.util package and extends java.util.AbstractSequentialList implements java.util.List interface
• Also, implements java.lang.Cloneable, java.io.Serializable marker interfaces which provides special ability to LinkedList (provided by JVM at run time) like,
• java.lang.Cloneable: to create a duplicate object or to clone an object
• java.io.Serializable: to transfer objects across network

Source: Team BenchResources.Net

2. LinkedList constructors:

2.1 LinkedList ll = new LinkedList();

• creates an empty LinkedList object

2.2 LinkedList ll = new LinkedList(Collection c);

• creates a LinkedList for the specified collection
• it is basically used for inter-conversion between collection objects

3. LinkedList methods:

• We can use LinkedList as Stack or Queue.
• To work with stack or queue,
• LinkedList defines more specific methods as listed below

4. LinkedList examples:

LinkedListAddAndRemove.java

package in.bench.resources.java.collection;

import java.util.LinkedList;

public class LinkedListAddAndRemove {

	public static void main(String[] args) {

		// creating LinkedList object of type String
		LinkedList<String> ll = new LinkedList<String>();

		// adding elements to LinkedList object
		ll.add("Sundar Pichai");
		ll.add("Satya Nadella");
		ll.add("Shiv Nadar");
		ll.add("Shantanu Narayen");
		ll.add("Sundar Pichai");
		ll.add("Francisco D’Souza");

		System.out.println("Iterating LinkedList values\n");

		// Iterating using enhanced for-loop
		for(String str : ll){
			System.out.println(str);
		}

		// removing element at 4th index
		ll.remove(4);

		// to print all values of LinkedList
		System.out.println("\n\nLinkedList values after removal"
				+ " at 4th index postion \n" + ll);
	}
}

Output:

Iterating LinkedList values

Sundar Pichai
Satya Nadella
Shiv Nadar
Shantanu Narayen
Sundar Pichai
Francisco D’Souza

LinkedList values after removal at 4th index postion
[Sundar Pichai, Satya Nadella, Shiv Nadar,
Shantanu Narayen, Francisco D’Souza]

Note: All methods of LinkedList is non-synchronized

Q) How to make LinkedList synchronized ?

• LinkedList can be easily converted into synchronized LinkedList using utility method of java.util.Collections class

List list = Collections.synchronizedList(ll);

Related Articles:

• List interface
• ArrayList class
• LinkedList class
• Vector class
• Stack class
• ArrayList v/s Vector
• ArrayList v/s LinkedList
• List v/s Set

References:

• https://docs.oracle.com/javase/tutorial/collections/intro/
• https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
• https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
• https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
• https://docs.oracle.com/javase/7/docs/api/java/util/LinkedList.html
• https://docs.oracle.com/javase/7/docs/api/java/util/List.html
• https://docs.oracle.com/javase/8/docs/api/java/util/List.html

Happy Coding !!
Happy Learning !!