In this tutorial, we have listed the top LinkedList program in Java for the best practices that will help you improve your coding skills.
All the LinkedList programs with explanation are based on the various operations, such as adding, removing, accessing, updating, getting elements, etc.
If you are preparing for a Java technical test and interview, then having a good understanding of LinkedList and its usage can give you a good advantage.
These example programs based on LinkedList are very important for beginners and freshers and will help you crack interviews.
Recommend that before going to practice all these programs, you must read the tutorial LinkedList in Java that is very helpful in understanding the concepts of LinkedList.
How to Add Element to LinkedList in Java?
Let’s take an example program where we will add elements in different ways using add(), add(int index, Object o), addFirst(Object o), addLast(Object o), addAll() methods of list interface and deque interface. Follow all steps in the example coding.
Program code 1:
package linkedListProgram;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Vector;
public class AddingExample
{
public static void main(String[] args)
{
// Create a LinkedList object.
LinkedList list = new LinkedList(); // empty linked list.
// Call add() method for adding Heterogeneous elements using reference variable list.
list.add("One");
list.add(2);
list.add(null); // null elements are allowed in the linked list.
list.add("Four");
System.out.println("Initial LinkedList order: " +list);
// Adding an element specified in the linked list.
list.add(3, "Three");
// Adding an element at the first position of list using addFirst() method of Deque interface.
System.out.println("LinkedList Elements after adding the first element");
list.addFirst("Zero");
System.out.println(list);
// Adding an element at the end of the list using addLast() method of Deque interface.
System.out.println("LinkedList Elements after adding the last element");
list.addLast("Five");
System.out.println(list);
// Adding all elements from existing ArrayList collection to the end of the LinkedList.
// Create an ArrayList object.
ArrayList al = new ArrayList();
al.add("Six");
al.add(7);
al.add("Eight");
// Call addAll() method to add all elements to the end of the linked list.
list.addAll(al);
System.out.println("LinkedList Elements after adding all elements from ArrayList");
System.out.println(list);
// Adding all elements from an existing Vector collection at the specified position of LinkedList.
Vector v = new Vector();
v.add(7.5);
v.add(7.8);
list.addAll(9, v);
System.out.println("Linkedlist elements after adding all elements from vector");
System.out.println(list);
}
}Output:
Initial LinkedList order:
[One, 2, null, Four]
LinkedList Elements after adding the first element
[Zero, One, 2, null, Three, Four]
LinkedList Elements after adding the last element
[Zero, One, 2, null, Three, Four, Five]
LinkedList Elements after adding all elements from ArrayList
[Zero, One, 2, null, Three, Four, Five, Six, 7, Eight]
Linked list Elements after adding all elements from the vector
[Zero, One, 2, null, Three, Four, Five, Six, 7, 7.5, 7.8, Eight]How to Remove Element from LinkedList in Java?
Let’s take an example program and see how to remove elements from the list in different ways using methods such as remove(), removeFirst(), removeLast().
Program code 2:
package linkedListProgram;
import java.util.ArrayList;
import java.util.LinkedList;
public class RemovingElementExample {
public static void main(String[] args)
{
// Create a generic LinkedList object of type String.
LinkedList<String> list = new LinkedList<String>();
int size = list.size();
System.out.println("Size of Linkedlist: " +size);
// Adding elements of String type.
list.add("Zero");
list.add("First");
list.add("Second");
list.add(null); // null elements are allowed in the linked list.
list.add("Fourth");
list.add("25");
System.out.println("Initial LinkedList order: " +list);
// Removing the first element from list using removeFirst() method.
list.removeFirst();
System.out.println("LinkedList Elements after removing the first element");
System.out.println(list);
// Removing the last element from the list using removeLast() method.
System.out.println("LinkedList Elements after removing the last element");
list.removeLast();
System.out.println(list);
// Removing element at the specified position from the list.
list.remove(2);
System.out.println("LinkedList Elements after removing the element at index position 2 ");
System.out.println(list);
// Adding all elements from existing an ArrayList collection to the end of LinkedList.
// Creating a generic ArrayList object of String type.
ArrayList<String> al = new ArrayList<String>();
al.add("Third");
al.add("Fourth");
list.addAll(2, al);
list.removeLastOccurrence("Fourth");
System.out.println("LinkedList Elements after removing last occurrence");
System.out.println(list);
}
}
A conceptual view of removing an element in LinkedList is shown in the below figure.
Output:
Size of LinkedList: 0
Initial LinkedList order: [Zero, First, Second, null, Fourth, 25]
LinkedList Elements after removing the first element
[First, Second, null, Fourth, 25]
LinkedList Elements after removing the last element
[First, Second, null, Fourth]
LinkedList Elements after removing the element at index position 2
[First, Second, Fourth]
LinkedList Elements after removing last occurrence
[First, Second, Third, Fourth]How to Get Element from LinkedList in Java?
Let’s take an example program in which we will get an element from the list in different ways using get(), getFirst(), and getLast() method.
Program code 3:
package linkedListProgram;
import java.util.LinkedList;
public class GetElementExample {
public static void main(String[] args)
{
// Create a LinkedList object.
LinkedList<Integer> list = new LinkedList<Integer>();
// Adding even numbers from 0 to 20 as elements in the list.
for(int i = 0 ; i < = 20; i++)
{
if(i % 2 == 0) // It will check even number.
list.add(i);
}
// Call getFirst() method to get first even number.
Object firstEvenNumber = list.getFirst(); // Return type of getFirst() methods is an Object.
System.out.println("First even number: " +firstEvenNumber);
Object lastEvenNumber = list.getLast();
System.out.println("Last even number: " +lastEvenNumber);
Object getElement = list.get(5);
System.out.println("Even number at index 5: " +getElement);
}
}Output:
First even number: 0
Last even number: 20
Even number at index 5: 10How to Retrieve and Remove Element in Java LinkedList?
We can retrieve and remove an element from LinkedList using peekFirst(), peekLast(), pollFirst(), and pollLast() methods.
1. peekFirst(): This method retrieves the first element from the list but does not remove the element from the list.
2. peekLast(): This method retrieves the last element from the list but does not remove it.
3. pollFirst(): This method retrieves and removes the first element from the list.
4. pollLast(): This method retrieves and removes the last element from the list.
Let’s write a program for it and use these methods.
Program code 4:
package linkedListExample;
import java.util.LinkedList;
public class PeakPollExample {
public static void main(String[] args)
{
// Create a LinkedList object.
LinkedList<String> list = new LinkedList<String>();
// Adding elements to the list.
list.add("INDIA");
list.add("USA");
list.add("JAPAN");
list.add("UK");
list.add("CANADA");
System.out.println("Initial LinkedList order");
System.out.println(list);
// Call peek() method to retrieve the first element from list.
Object firstElement = list.peekFirst(); // Return type of this method is an Object.
System.out.println("Retrieve the first element: " +firstElement);
Object lastElement = list.peekLast();
System.out.println("Retrieve the last element: " +lastElement);
// Call pollLast() to retrieve and remove the last element from the list.
Object element1 = list.pollLast();
System.out.println("Retrieve and remove the last element: " +element1);
System.out.println("LinkedList Element after using pollLast() method");
System.out.println(list);
}
}Output:
Initial LinkedList order
[INDIA, USA, JAPAN, UK, CANADA]
Retrieve the first element: INDIA
Retrieve the last element: CANADA
Retrieve and remove the last element: CANADA
LinkedList Element after using pollLast() method
[INDIA, USA, JAPAN, UK]How to Pop and Push Element from and onto stack in Java LinkedList?
Pop() method: This method is equivalent to removeFirst() method that removes and returns the first element from the list. In other words, It pops an element from the stack represented by the list.
Push() method: This method is equivalent to addFirst() method that adds an element at the first position of the list. In other words, It pushes an element onto the stack represented by the list.
Let’s write a Java program in which we will pop and push an element from and onto stack in LinkedList.
Program code 5:
package linkedListProgram;
import java.util.LinkedList;
public class PeakPollExample {
public static void main(String[] args)
{
LinkedList<Character> list = new LinkedList<Character>();
// Adding elements in the list.
list.add('A');
list.add('B');
list.add('C');
list.add('D');
list.add('E');
System.out.println("Initial LinkedList order");
System.out.println(list);
Object element = list.pop(); // Return type of this method is an Object.
System.out.println("Pops Element: " +element);
list.push('B');
System.out.println("LinkedList Element after pushing");
System.out.println(list);
}
}Output:
Initial LinkedList order
[A, B, C, D, E]
Pops Element: A
LinkedList Element after pushing
[B, B, C, D, E]Hope that this tutorial has covered all the important linkedlist example program in Java. All linked list programs are very important to clear concepts for beginners. I hope that you will have understood example programs and practiced them.
Thanks for reading!!!Next ⇒ How to iterate LinkedList in Java