Java Deque addFirst() Method with Examples

by Online Tutorials Library July 22, 2022

Java Deque addFirst() Method

The addFirst() method of Java Deque Interface is used to insert the specified element at the front of the deque .

Syntax:

Parameter:

The above method consists of only one parameter:

The element ‘e’ that needs to be added.

Return:

Throw:

IllegalStateException– If the elements cannot be added at the time due to capacity restriction.

ClassCastException– If the class of the specified element avoids it from being added to the deque.

NullPointerException– If the specified element is a null and the deque does not allow the null elements.

IllegalArgumentException– If some of the property of the given element avoids it from being added to the deque.

Example 1

  import java.util.ArrayDeque;  import java.util.Deque;  public class JavaDequeaddFirstExample1 {       public static void main(String[] args) {  Deque<Integer> deque = new ArrayDeque<>();  deque.addFirst(44);  deque.addFirst(33);  deque.addFirst(22);  deque.addFirst(11);      System.out.println(“The elements are adding at the front of the deque : “+deque);      }  }  

Test it Now

Output:

The elements are adding at the front of the deque : [11, 22, 33, 44]

Example 2

  import java.util.ArrayDeque;  import java.util.Deque;  import java.util.Scanner;    public class JavaDequeaddFirstExample2 {     public static void main(String[] args) {     Deque<String> deque = new ArrayDeque<>();  deque.addFirst(“FAT”);  deque.addFirst(“CAO”);  deque.addFirst(“JAVA”);  deque.addFirst(“DBMS”);     System.out.println(“The subjects are given as : “+deque);        }  }  

Output:

The subjects are given as : [DBMS, JAVA, CAO, FAT]

Example 3

  import java.util.ArrayDeque;  import java.util.Deque;  import java.util.Scanner;    public class JavaDequeaddFirstExample3 {     public static void main(String[] args) {   System.out.print(“Enter the number of times you want to enter the names : “);   Scanner scanner = new Scanner(System.in);   int n = scanner.nextInt();     Deque<String> deque = new ArrayDeque<String>();   System.out.println(“The names are : “);   for (int i = 0; i < n; i++) {    String name = scanner.next();    deque.addFirst(name);    }   System.out.println(“The final deque is : “+deque);     }  }  

Output:

Enter the number of times you want to enter the names : 4  The names are :   Sham  Ram  Stuti  Ranajna  The final deque is : [Ranajna, Stuti, Ram, Sham]

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Java Deque addFirst() Method with Examples

Java Deque addFirst() Method

Syntax:

Parameter:

Return:

Throw:

Example 1

Example 2

Example 3

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