Java program to add elements to LinkedList

LinkedList is a general class of Java Collection Framework, which implements three interfaces: List, Deque and Queue. It provides the functionality of the LinkedList data structure, a linear data structure in which each element is linked to each other. We can perform a variety of operations on a LinkedList, including adding, removing, and traversing elements. To add elements to a LinkedList collection, we can use various built-in methods such as add(), addFirst(), and addLast(). We'll explore how to use these methods to add elements to a LinkedList.

Add elements to LinkedList in Java

In Java, the LinkedList class provides the following built-in methods to add elements -

• add() − It is used to insert an element at the end of the collection. We use it more frequently than other methods.

• addFirst() − This method is used to insert an element at the first index of LinkedList.

• addLast() − It inserts an element into the last index position of the specified LinkedList.

• addAll() − When we need to add all elements of a collection to another LinkedList, we use the addAll() method.

In our Java program, while inserting elements into LinkedList, we just pass the required elements as parameters.

Before jumping to the Java program to add elements to a LinkedList, let us discuss the syntax for creating an instance of the LinkedList class.

grammar

LinkedList<Type> nameOfinstance = new LinkedList<>();

Here, 'Type' can be any wrapper class.

The Chinese translation of

Example 1

is:

Example 1

The following example illustrates how we use the add() method to insert elements into a LinkedList.

import java.util.LinkedList;
public class Demo1 {
   public static void main(String[] args) {
      // creating a linkedlist 
      LinkedList<String> input_list = new LinkedList<>();
      // adding elements to the list
      input_list.add("Java");
      input_list.add("Python");
      input_list.add("Scala");
      input_list.add("Shell");
      // printing the result
      System.out.println("The elements added to the list are: " + input_list);
   }
}

Output

The elements added to the list are: [Java, Python, Scala, Shell]

Example 2

You can also use the add() method to insert elements at the desired position in LinkedList. It can also accept an index number as an optional argument.

import java.util.LinkedList;
public class Demo2 {
   public static void main(String[] args) {
      // creating a linkedlist 
      LinkedList<String> input_list = new LinkedList<>();
      // adding initial elements to the list
      input_list.add("Java");
      input_list.add("Python");
      input_list.add("JavaScript");
      // printing the result
      System.out.println("The list is defined as: " + input_list);
      // adding a new element to the existing list at index 1
      input_list.add(1, "Scala");
      // printing the new result
      System.out.println("The list after adding element at position 1: ");
      int index = 0;
      for(String print : input_list) {
         System.out.println("Index: " + index + ", Element: " + print);
         index++;
      }
   }
}

Output

The list is defined as: [Java, Python, JavaScript]
The list after adding element at position 1: 
Index: 0, Element: Java
Index: 1, Element: Scala
Index: 2, Element: Python
Index: 3, Element: JavaScript

Example 3

In the following example, we will use the listIterator() method to add elements to a LinkedList.

import java.util.LinkedList;
import java.util.ListIterator;
public class Demo3 {
   public static void main(String[] args) {
      // creating a linkedlist 
      LinkedList<String> input_list = new LinkedList<>();
      // creating an instance of ListIterator
      ListIterator<String> newList = input_list.listIterator();
      // adding elements to the list
      newList.add("Java");
      newList.add("Python");
      newList.add("Scala");
      newList.add("Shell");
      // printing the result
      System.out.println("The elements added to the list are: " + input_list);
   }
}

Output

The elements added to the list are: [Java, Python, Scala, Shell]

The Chinese translation of

Example 4

is:

Example 4

In this example, we will use the addFirst() and addLast() methods to insert elements at the first and last index of the LinkedList.

import java.util.LinkedList;
public class Demo4 {
   public static void main(String[] args) {
      LinkedList<Integer> inputList = new LinkedList<>();
      // Adding elements in linkedlist
      inputList.add(8);
      inputList.add(4);
      inputList.add(1);
      inputList.add(0);
      System.out.println("Elements of the original Linkedlist : " + inputList);
      // adding elements to the first and last index
      inputList.addFirst(9);
      inputList.addLast(9);
      // to print the result
      System.out.println("After adding elements to the first and last index of Linkedlist : " + inputList);
   }
}

Output

Elements of the original Linkedlist : [8, 4, 1, 0]
After adding elements to the first and last index of Linkedlist : [9, 8, 4, 1, 0, 9]

in conclusion

This article first introduces LinkedList, which is a common class of Java Collection Framework. In the next section, we saw various built-in methods of this class that can be used to insert elements into a LinkedList collection. These methods are: add(), addAll(), addFirst(), and addLast().

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