Java Deque peekFirst() Method with Examples

by Online Tutorials Library July 22, 2022

Java Deque peekFirst() Method

The peekFirst() method of Java Deque Interface retrieves and not remove the first element of the given deque. But, if the deque is empty, it may return null.

Syntax:

Parameter:

N.A.

Return:

The above method is used to return the head of the given deque. On the other hand, if the deque is empty, the method may return null.

Example 1

  import java.util.ArrayDeque;  import java.util.Deque;  public class JavaDequepeekFirstExample1 {     public static void main(String[] args) {     Deque<String> deque = new ArrayDeque<>();    deque.offer(“Tina”);    deque.offer(“Shyam”);    deque.offer(“Isha”);    deque.offer(“Falguni”);    String val = deque.peekFirst();  System.out.println(“The first value is given as : “+val);     System.out.println(“The deque is given as : “+deque);  }  }  

Test it Now

Output:

The first value is given as : Tina  The deque is given as : [Tina, Shyam, Isha, Falguni]

Example 2

  import java.util.ArrayDeque;  import java.util.Deque;  public class JavaDequepeekFirstExample2 {      public static void main(String[] args) {      Deque<Integer> deque = new ArrayDeque<>();      deque.offer(34);      deque.offer(43);      deque.offer(22);      deque.offer(55);      int val = deque.peekFirst();    System.out.println(“The first integer value is given as : “+val);   System.out.println(“The deque is given as : “+deque);     }     }  

Test it Now

Output:

The first integer value is given as : 34  The deque is given as : [34, 43, 22, 55]

Example 3

  import java.util.ArrayDeque;  import java.util.Deque;  public class JavaDequepeekFirstExample3 {     public static void main(String[] args) {     Deque<Character> deque = new ArrayDeque<>();    deque.offer(‘H’);    deque.offer(‘E’);    deque.offer(‘L’);    deque.offer(‘L’);    deque.offer(‘O’);    Character val = deque.peekFirst();    System.out.println(“The first characater value is given as : “+val);  System.out.println(“The final deque is given as : “);      for (Character character : deque) {  System.out.println(character);      }       }    }  

Test it Now

Output:

The first characater value is given as : H  The final deque is given as :   H  E  L  L  O

Next TopicJava Deque

add()addAll()addfirst()addlast()contains()descendingiterator()element()getfirst()getlast()iterator java deque java tutorial methods offer()offerfirst()offerlast()peek()peekfirst()peeklast()poll()pollfirst()polllast()

Java Deque peekFirst() Method with Examples

Java Deque peekFirst() Method

Syntax:

Parameter:

Return:

Example 1

Example 2

Example 3

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