LinkedList Class In Java

LinkedList Class In Java: A LinkedList has a group of elements in the form of nodes. Each node has three fields where the data field contains the data, and the link fields reference the previous and next nodes.

The Java LinkedList class implements the list interface.

LinkedList is very convenient to store the data. Inserting the elements into the LinkedList and removing them from the LinkedList is done quickly; that’s why it is preferred over the arrays.

LinkedList also has some disadvantages, like the nodes can not be directly like in an array; we are accessing an element by using its index. Here, we need to start from the head and follow through the link to reach a node we can access.

To store the elements in a linked list, we use a double-linked list, which provides a linear data structure and is also used to inherit an abstract class and implement list and deque interfaces.

Important Methods Of LinkedList

  • It can contain duplicate elements.
  • The insertion is preserved.
  • Java LinkedList class is non-synchronized.
  • Null Insertion is possible.
  • Duplicate and Heterogeneous elements are allowed.
  • LinkedList implements the Serializable and Cloneable interfaces but not the random access interface.
  • LinkedList is the best choice if your frequent operation is insertion and deletion in the middle, and if your frequent operation is retrieval, then don’t use LinkedList; that time, you can use ArrayList.
  • The underlying data structure for LinkedList is a double-linked list.

Constructors for Java LinkedList

The LinkedList class also has various methods and constructors like other Java collections. The LinkedList class has two constructors that are:

  • LinkedList(): Used to create an empty linked list.
  • LinkedList(Collection C): Used to create an ordered list that contains all the elements of a specified collection, as returned by the collection’s iterator.

LinkedList Class Methods

How do you verify Element Presence LinkedList Java with an example?

package com.java.Softwaretestingblog;
import java.util.LinkedList;
import java.util.List;
public class VerifyLinkedListElement {
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      //www.softwaretestingblog.in
      LinkedList<String> arrl = new LinkedList<String>();
        arrl.add("First");
        arrl.add("Second");
        arrl.add("Third");
        arrl.add("Random");
        List<String> list = new LinkedList<String>();
        list.add("Second");
        list.add("Random");
        System.out.println("Does LinkedList contains all list elements?: "+arrl.containsAll(list));
        list.add("one");
        System.out.println("Does LinkedList contains all list elements?: "+arrl.containsAll(list));
   }
}

Output:

Does LinkedList contains all list elements?: true
Does LinkedList contains all list elements?: false

How To Get All Values LinkedList HasNext() In Java With Example?

package com.java.Softwaretestingblog;
import java.util.LinkedList;
public class LastElementLinkedList {
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      //www.softwaretestingblog.in
      LinkedList<String> arrl = new LinkedList<String>();
        arrl.add("First");
        arrl.add("Second");
        arrl.add("Third");
        arrl.add("Random");
        System.out.println("Last Element: "+arrl.getLast());
        System.out.println("Last Element: "+arrl.peekLast());
   }
}

Output:

Last Element: Random
Last Element: Random

Write a program to get the first element of LinkedList Java with an example.

package com.java.Softwaretestingblog;
import java.util.LinkedList;
public class GetFirstElementLinkedListJava {
   public static void main(String[] args) {
   // TODO Auto-generated method stub
   //www.softwaretestingblog.in
   LinkedList<String> arrl = new LinkedList<String>();
        arrl.add("First");
        arrl.add("Second");
        arrl.add("Third");
        arrl.add("Random");
        System.out.println("First Element: "+arrl.element());
        System.out.println("First Element: "+arrl.getFirst());
        System.out.println("First Element: "+arrl.peek());
        System.out.println("First Element: "+arrl.peekFirst());
   }
}

Output:

First Element: First
First Element: First
First Element: First
First Element: First

Write a Program to Clear LinkedList Values In Java With Example?

package com.java.Softwaretestingblog;
import java.util.LinkedList;
public class ClearMyLinkedList {
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      //www.softwaretestingblog.in
      LinkedList<String> arrl = new LinkedList<String>();
      //adding elements to the end
      arrl.add("First");
      arrl.add("Second");
      arrl.add("Third");
      arrl.add("Random");
      System.out.println("Actual LinkedList:"+arrl);
      arrl.clear();
      System.out.println("After clear LinkedList:"+arrl);
   }
}

Output:

Actual LinkedList:[First, Second, Third, Random]
After clear LinkedList:[]

How do you reverse LinkedList value using collections in Java with examples?

package com.java.Softwaretestingblog;
import java.util.Collections;
import java.util.LinkedList;
public class Reverse_Value_LinkedList {
   public static void main(String[] args) {
   // TODO Auto-generated method stub
   //www.softwaretestingblog.in
   LinkedList<String> list = new LinkedList<String>();
        list.add("Java");
        list.add("Cric");
        list.add("Play");
        list.add("Watch");
        list.add("Glass");
        Collections.reverse(list);
        System.out.println("Results after reverse operation:");
        for(String str: list)
        {
            System.out.println(str);
        }
   }
}

Output:

Results before reverse operation:
Java
Cric
Play
Watch
Glass
Results after reverse operation:
Glass
Watch
Play
Cric
Java

Please write comments if you find anything incorrect or if you want to share more information about the above-mentioned topic.

Different Ways to Remove Elements LinkedList In Java With Example?

package com.softwaretestingo.java.basics;
import java.util.LinkedList;
public class RemoveFromLinkedList 
{
   public static void main(String[] args) 
   {
      LinkedList<String> arrl = new LinkedList<String>();
      arrl.add("First");
      arrl.add("Second");
      arrl.add("Third");
      arrl.add("Random");
      arrl.add("four");
      arrl.add("five");
      arrl.add("six");
      arrl.add("seven");
      arrl.add("eight");
      arrl.add("nine");
      System.out.println(arrl);
      System.out.println("Remov() method:"+arrl.remove());
      System.out.println("After remove() method call:");
      System.out.println(arrl);
      System.out.println("remove(index) method:"+arrl.remove(2));
      System.out.println("After remove(index) method call:");
      System.out.println(arrl);
      System.out.println("Remov(object) method:"+arrl.remove("six"));
      System.out.println("After remove(object) method call:");
      System.out.println(arrl);
      System.out.println("removeFirst() method:"+arrl.removeFirst());
      System.out.println("After removeFirst() method call:");
      System.out.println(arrl);
      System.out.println("removeFirstOccurrence() method:" +arrl.removeFirstOccurrence("eight"));
      System.out.println("After removeFirstOccurrence() method call:");
      System.out.println(arrl);
      System.out.println("removeLast() method:"+arrl.removeLast());
      System.out.println("After removeLast() method call:");
      System.out.println(arrl);
      System.out.println("removeLastOccurrence() method:"+ arrl.removeLastOccurrence("five"));
      System.out.println("After removeLastOccurrence() method call:");
      System.out.println(arrl);
   }
}

Output:

[First, Second, Third, Random, four, five, six, seven, eight, nine]
Remov() method:First
After remove() method call: [Second, Third, Random, four, five, six, seven, eight, nine]
remove(index) method:Random
After remove(index) method call: [Second, Third, four, five, six, seven, eight, nine]
Remov(object) method:true
After remove(object) method call: [Second, Third, four, five, seven, eight, nine]
removeFirst() method:Second
After removeFirst() method call: [Third, four, five, seven, eight, nine]
removeFirstOccurrence() method:true
After removeFirstOccurrence() method call: [Third, four, five, seven, nine]
removeLast() method:nine
After removeLast() method call: [Third, four, five, seven]
removeLastOccurrence() method:true
After removeLastOccurrence() method call: [Third, four, seven]

Please comment if you find anything incorrect or want to share more information about the topic discussed above.

How do you add values to the last LinkedList in Java with an example?

package com.java.Softwaretestingblog;
import java.util.LinkedList;
public class Add_Values_Last_LinkedList {
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      //www.softwaretestingblog.in
      LinkedList<String> arrl = new LinkedList<String>();
        arrl.add("First");
        arrl.add("Second");
        arrl.add("Third");
        arrl.add("Random");
        System.out.println(arrl);
        System.out.println("Adding element at last position...");
        arrl.addLast("I am last");
        System.out.println(arrl);
        System.out.println("Adding element at last position...");
        arrl.offerLast("I am last - 1");
        System.out.println(arrl);
        System.out.println("Adding element at last position...");
        arrl.offer("I am last - 2");
        System.out.println(arrl);
   }
}

Output:

[First, Second, Third, Random]
Adding element at last position...
[First, Second, Third, Random, I am last]
Adding element at last position...
[First, Second, Third, Random, I am last, I am last - 1]
Adding element at last position...
[First, Second, Third, Random, I am last, I am last - 1, I am last - 2]

Please comment if you find anything incorrect or want to share more information about the topic discussed above.

Different Basic Methods LinkedList In Java With Example?

package com.softwaretestingo.java.basics;
import java.util.LinkedList;
public class LinkedListOperations 
{
   public static void main(String[] args) 
   {
      LinkedList<String> ll = new LinkedList<String>();
      ll.add("Orange");
      ll.add("Apple");
      ll.add("Grape");
      ll.add("Banana");
      System.out.println(ll);
      System.out.println("Size of the linked list: "+ll.size());
      System.out.println("Is LinkedList empty? "+ll.isEmpty());
      System.out.println("Does LinkedList contains 'Grape'? "+ll.contains("Grape"));
   }
}

Output:

[Orange, Apple, Grape, Banana]
Size of the linked list: 4
Is LinkedList empty? false
Does LinkedList contains 'Grape'? true

Please write comments if you find anything incorrect or if you want to share more information about the above-mentioned topic.

First LinkedList Value Using Java: Write a Program to Add Values First LinkedList In Java?

package com.java.Softwaretestingblog;
import java.util.LinkedList;
public class Add_Values_First_LinkedList {
   public static void main(String[] args) {
      // TODO Auto-generated method stub
      LinkedList<String> arrl = new LinkedList<String>();
      arrl.add("First");
      arrl.add("Second");
      arrl.add("Third");
      arrl.add("Random");
      System.out.println(arrl);
      System.out.println("Adding element at first position...");
      arrl.addFirst("I am first");
      System.out.println(arrl);
      System.out.println("Adding element at first position...");
      arrl.offerFirst("I am first - 2");
      System.out.println(arrl);
   }
}

Output:

[First, Second, Third, Random]
Adding element at first position...
[I am first, First, Second, Third, Random]
Adding element at first position...
[I am first - 2, I am first, First, Second, Third, Random]

Please write comments if you find anything incorrect or if you want to share more information about the above-mentioned topic.

Another LinkedList Java Program: How do you copy values from one list to another LinkedList Java with an example?

package com.java.Softwaretestingblog;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
public class Copyvalues2LinkedlistinJava {
   public static void main(String[] args) {
   // TODO Auto-generated method stub
   //www.softwaretestingblog.in
   LinkedList<String> arrl = new LinkedList<String>();
        //adding elements to the end
        arrl.add("First");
        arrl.add("Second");
        arrl.add("Third");
        arrl.add("Random");
        System.out.println("Actual LinkedList:"+arrl);
        List<String> list = new ArrayList<String>();
        list.add("one");
        list.add("two");
        arrl.addAll(list);
        System.out.println("After Copy: "+arrl);
   }
}

Output:

Actual LinkedList:[First, Second, Third, Random]
After Copy: [First, Second, Third, Random, one, two]

Please write comments if you find anything incorrect or if you want to share more information about the above-mentioned topic.

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I love open-source technologies and am very passionate about software development. I like to share my knowledge with others, especially on technology that's why I have given all the examples as simple as possible to understand for beginners. All the code posted on my blog is developed, compiled, and tested in my development environment. If you find any mistakes or bugs, Please drop an email to softwaretestingo.com@gmail.com, or You can join me on Linkedin.

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