Deque element() method in Java - GeeksforGeeks

19 Dec, 2021
The element() method of Deque Interface returns the element at the front the container. It does not deletes the element in the container. This method returns the head of the Deque. The method throws an exception when the Deque is empty. Syntax:  
E element()
Parameters: This method does not accepts any parameter.Returns: This method returns the element at the front the container or the head of the Deque.Exception: The function throws NoSuchElementException when the Deque is empty and the function is called. Below programs illustrate element() method of Deque:Program 1: With the help of LinkedList.  
Java
// Java Program Demonstrate element()// method of Dequeimport java.util.*; public class GFG {    public static void main(String[] args)        throws IllegalStateException    {         // create object of Deque        Deque<Integer> DQ            = new LinkedList<Integer>();         // Add numbers to end of Deque        DQ.add(7855642);        DQ.add(35658786);        DQ.add(5278367);        DQ.add(74381793);         // print Deque        System.out.println("Deque: " + DQ);         // print head        System.out.println("Deque's head: " + DQ.element());    }}
Deque: [7855642, 35658786, 5278367, 74381793]
Deque's head: 7855642
 
Program 2: With the help of ArrayDeque. 
Java
// Java Program Demonstrate element()// method of Dequeimport java.util.*; public class GFG {    public static void main(String[] args)        throws IllegalStateException    {         // create object of Deque        Deque<Integer> DQ            = new ArrayDeque<Integer>();         // Add numbers to end of Deque        DQ.add(7855642);        DQ.add(35658786);        DQ.add(5278367);        DQ.add(74381793);         // print Deque        System.out.println("Deque: " + DQ);         // print head        System.out.println("Deque's head: " + DQ.element());    }}
Deque: [7855642, 35658786, 5278367, 74381793]
Deque's head: 7855642
 
Program 3: With the help of ConcurrentLinkedDeque. 
Java
// Java Program Demonstrate element()// method of Dequeimport java.util.*;import java.util.concurrent.ConcurrentLinkedDeque; public class GFG {    public static void main(String[] args)        throws IllegalStateException    {         // create object of Deque        Deque<Integer> DQ            = new ConcurrentLinkedDeque<Integer>();         // Add numbers to end of Deque        DQ.add(7855642);        DQ.add(35658786);        DQ.add(5278367);        DQ.add(74381793);         // print Deque        System.out.println("Deque: " + DQ);         // print head        System.out.println("Deque's head: " + DQ.element());    }}
Deque: [7855642, 35658786, 5278367, 74381793]
Deque's head: 7855642
 
Program 4: With the help of LinkedBlockingDeque. 
Java
// Java Program Demonstrate element()// method of Dequeimport java.util.*;import java.util.concurrent.LinkedBlockingDeque; public class GFG {    public static void main(String[] args)        throws IllegalStateException    {         // create object of Deque        Deque<Integer> DQ            = new LinkedBlockingDeque<Integer>();         // Add numbers to end of Deque        DQ.add(7855642);        DQ.add(35658786);        DQ.add(5278367);        DQ.add(74381793);         // print Deque        System.out.println("Deque: " + DQ);         // print head        System.out.println("Deque's head: " + DQ.element());    }}
Deque: [7855642, 35658786, 5278367, 74381793]
Deque's head: 7855642
 
Program 2: 
Java
// Java Program Demonstrate element()// method of Dequeimport java.util.*; public class GFG {    public static void main(String[] args)        throws IllegalStateException    {         // create object of Deque        Deque<Integer> DQ            = new LinkedList<Integer>();         // Add numbers to end of Deque        DQ.add(7855642);        DQ.add(35658786);        DQ.add(5278367);        DQ.add(74381793);         // print Deque        System.out.println("Deque: " + DQ);         // print head        System.out.println("Deque's head: " + DQ.element());         DQ.clear();         // Deque is empty now hence exception        System.out.println("Deque's head: " + DQ.element());    }}
Output: 
Exception in thread "main" java.util.NoSuchElementException
    at java.util.LinkedList.getFirst(LinkedList.java:244)
    at java.util.LinkedList.element(LinkedList.java:663)
    at GFG.main(GFG.java:29)
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html#element–
anikaseth98
Java - util package
java-deque
Java-Functions
Java
Java
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