The java.util.concurrent.ConcurrentLinkedDeque.peekFirst() is an in-built method in Java which
retrieves the first element of this deque without removing it. The function returns NULL if the deque is empty.
Syntax:
Conn_Linked_Deque.peekFirst()
Parameters: This function does not accepts any parameter.
Return Values: The function returns the first element present in this deque and returns NULL when the deque is empty.
Below programs illustrate the peekFirst() method:
Program 1: This program involves deque with Integer elements.
// Java Program Demonstrate peekFirst() // method of ConcurrentLinkedDeque import java.util.concurrent.*;
class ConcurrentLinkedDequeDemo {
public static void main(String[] args)
{
ConcurrentLinkedDeque<Integer> cld =
new ConcurrentLinkedDeque<Integer>();
cld.addFirst( 12 );
cld.addFirst( 110 );
cld.addFirst( 55 );
cld.addFirst( 76 );
// Displaying the existing LinkedDeque
System.out.println( "Elements in"
+ "the LinkedDeque: " + cld);
// Displaying the first element
System.out.println( "First Element in"
+ "the LinkedDeque: " + cld.peekFirst());
}
} |
Output:
Elements inthe LinkedDeque: [76, 55, 110, 12] First Element inthe LinkedDeque: 76
Program 2: This program involves deque with String elements.
// Java Program Demonstrate peekFirst() // method of ConcurrentLinkedDeque import java.util.concurrent.*;
class ConcurrentLinkedDequeDemo {
public static void main(String[] args)
{
ConcurrentLinkedDeque<String> cld =
new ConcurrentLinkedDeque<String>();
cld.addFirst( "GFG" );
cld.addFirst( "Gfg" );
cld.addFirst( "GeeksforGeeks" );
cld.addFirst( "Geeks" );
// Displaying the existing LinkedDeque
System.out.println( "Elements in"
+ "the LinkedDeque: " + cld);
// Displaying the First element
System.out.println( "First Element in"
+ "the LinkedDeque: " + cld.peekFirst());
}
} |
Output:
Elements inthe LinkedDeque: [Geeks, GeeksforGeeks, Gfg, GFG] First Element inthe LinkedDeque: Geeks