Java LinkedList Class

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Java LinkedList Class | What is LinkedList Class in Java Collecton?

Hello Readers in this article we are going to learn about JAVA
Collection LinkedList Class.

LinkedList Class in JAVA Collection is a Class which can be used to hold heterogeneous types of elements as Array allowed only homogeneous type of elements and it is fixed in size.

To overcome these problem we should go for Java Collection who provide several classes.Here we are looking for LinkedList Class.


Declaration/Hierarchy of Java Collection LinkedList  Class.

public class LinkedList<E>  extends AbstractSequentialList<E>

implements List<E>, Deque<E>, Cloneable, java.io.Serializable


LinkedList Class
The underlying data structure is doubly linked list.
It uses doubly linked list to store the elements.
In doubly Linked List case we add or remove elements from both side.
Insertion order is preserved.
It allows duplicate elements to be stored.
It allows null also.
     It is not implements Random Access.
     It better for to perform manipulation in between.

     It is not recommended to perform retrieval operations.

Capacity concept not applicable in the case of LinkedList.

Java LinkedList Class is not Synchronized.

LinkedList extends AbstractSequentialList<E>implements List<E>, Deque<E>, Cloneable, java.io.Serializable.


Constructors of LinkedList Class.

1.LinkedList();

It creates an empty LinkedList.

2.LinkedList(Collection c);

It is used to creates an equivalent LinkedList object for the
given or specified Collection.


Method's

boolean add(Object o)  

It is used to add the specified element to the end of a list.

void add(int index, Object element)  

It is used to add the elements at the specified index in list.

void addFirst(Object o) 

It is used to add element at the starting of a list.

void addLast(Object o)  

It is used to add the element to the end of a list.

Object getFirst()              

It is used to return the first element from a list.

Object getLast()              

It is used to return the last element from a list.

boolean contains(Object o)    

It is used to return true if the list contains the given element.

boolean remove(Object o) 

It is used to remove the first occurrence of the specified element from a list.

int indexOf(Object o)     

It is used to returns the index from a list of the first occurrence of the given element, it will return -1 if the list does not contain given element.

int lastIndexOf(Object o)             

It is used to return the index in a list of the last occurrence of the given element, or it will return -1 if the list does not contain given element.

int size()               

It is used to return the size/number of elements present in a list.


Java LinkedList Examples

In this example we will learn.

How to add elements in LinkedList?

How to print the elements of LinkedList?

How to get first element?

How to get last element?

How to get size of LinkedList?

How to get first occurrence of elements?

How to get last occurrence of elements?

How to check this list contains specific element?

How to remove elements?

How to remove first element from LinkedList?

How to remove last element LinkedList?

How to add elements of LinkedList to another LinkedList using addAll(Collection c) method?

How to add element at first index in LinkedList using addFirst() method?

How to add element at last index in LinkedList using addLast() method?

How to get elements of LinkedList one by one?

import java.util.*;

public class TestLinkedList{

public static void main(String[] args){

LinkedList<String> ll=new LinkedList<String>();

ll.add("Matin");

ll.add("Kishan");

ll.add("Dilshad");

ll.add("Manish");

ll.add("Chandan");

ll.add("Matin");

System.out.println("Normal Linked List");

System.out.println(ll);

         

System.out.println("Getting 1st Eement");

System.out.println(ll.getFirst());

          

System.out.println("Getting last Eement");

System.out.println(ll.getLast());

          

System.out.println("Size of list "+ll.size());


System.out.println("First Occurrence of Matin "+ll.indexOf("Matin"));

System.out.println("Lasst Occurrence of Matin "+ll.lastIndexOf("Matin"));


System.out.println("Is this list contains Kishan "+ll.contains("Kishan"));

System.out.println("Is list contains Kunal "+ll.contains("kunal"));

          

ll.remove("Manish");//removing manish

System.out.println(ll);

          

ll.removeFirst();//removing first element

System.out.println(ll);

ll.removeLast();//removing last element

System.out.println(“After removeFirst() and removeLast() ”+ll);

          

LinkedList<String> ls=new LinkedList<>();

ls.add("Cricket");

ls.add("FootBall");

ll.addAll(ls);//adding ls to ll at the end of ll

ll.addFirst("First Element");//adding to first in ll

ll.addLast("Last Element");");//adding to lasst in ll


System.out.println("After Addition of ls now Normal Linked List "+ll);


//Getting List elements one by one

System.out.println("Getting List Elements one by one");

for(String s:ll){

System.out.println(s);

            }

      }//end of main

}//end of class

output:

Normal Linked List

[Matin, Kishan, Dilshad, Manish, Chandan, Matin]

Getting 1st Eement

Matin

Getting last Eement

Matin

Size of list 6

First Occurrence of Matin 0

Lasst Occurrence of Matin 5

Is this list contains Kishan true

Is list contains Kunal false

[Matin, Kishan, Dilshad, Chandan, Matin]

[Kishan, Dilshad, Chandan, Matin]

After removeFirst() and removeLast()[Kishan, Dilshad, Chandan]

After Addition of ls now Normal Linked List [First Element, Kishan, Dilshad, Chandan, Cricket, FootBall, Last Element]

Getting List Elements one by one

First Element

Kishan

Dilshad

Chandan

Cricket

FootBall

Last Element


Java SportsLinkedList Examples
In this example we will see how to add user defined class object into LinkedList, first we have created a class named as SportLinkedList with id,sportname and city name and a parameterized constructor.

We have overridden a toString() method fot textual representation of object.After that we have created the object of SportLinkedList class by passing the required arguments and added then to LinkedList using add() method and displaying them.

import java.util.*;

public class SportLinkedList {

int id;

String sportname,cityname;

public SportLinkedList(int id, String sportname, String cityname) {

this.id = id;

this.sportnamesportname;

this.citynamecityname;

}

@Override

public String toString() {

return id + "," + sportname + "," + cityname;

}

//Main Method

public static void main(String[] args) {

SportLinkedList sll1=new SportLinkedList(1, "Cricket", "Mumbai"); 

 SportLinkedList sll2=new SportLinkedList(2, "FootBall", "Assam"); 

 SportLinkedList sll3=new SportLinkedList(3, "Hockey", "Punjab"); 

LinkedList<SportLinkedList> ll=new LinkedList<SportLinkedList>(); 

ll.add(sll1);

ll.add(sll2); 
 ll.add(sll3);  
System.out.println("id Sport City");  
for(SportLinkedList ss:ll) {  System.out.println(ss);                      }

  }//End of main

}//End of class 

Output: 
id   Sport   City 1,Cricket,Mumbai2,FootBall,Assam 3,Hockey,Punjab


Hope it was helpful
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