The getFirst() method of LinkedBlockingDeque returns the front most element in the Deque container. If the LinkedBlockingDeque is empty, then on function call it returns a NoSuchElementException.
Syntax:
public E getLast()
Parameters: This method does not accept any parameters.
Returns: This method returns the first element or the head of this Deque container.
Exception: The function throws only one exception i.e., NoSuchElementException when the deque is empty
Below programs illustrate getFirst() method of LinkedBlockingDeque:
Program 1:
// Java Program Demonstrate getFirst() // method of LinkedBlockingDeque import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
// create object of LinkedBlockingDeque
LinkedBlockingDeque<Integer> LBD
= new LinkedBlockingDeque<Integer>();
// Add numbers to front of LinkedBlockingDeque
LBD.addFirst( 7855642 );
LBD.addFirst( 35658786 );
LBD.addFirst( 5278367 );
LBD.addFirst( 74381793 );
// before removing print queue
System.out.println( "Linked Blocking Deque: " + LBD);
// prints the first element
System.out.println( "Linked Blocking Deque first element: " +
LBD.getFirst());
}
} |
Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642] Linked Blocking Deque first element: 74381793
Program 2:
// Java Program Demonstrate getFirst() // method of LinkedBlockingDeque import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
// create object of LinkedBlockingDeque
LinkedBlockingDeque<Integer> LBD
= new LinkedBlockingDeque<Integer>();
// Add numbers to front of LinkedBlockingDeque
LBD.addFirst( 7855642 );
LBD.addFirst( 35658786 );
LBD.addFirst( 5278367 );
LBD.addFirst( 74381793 )
LBD.clear();
// Since the container is empty it will throw exception
System.out.println( "Linked Blocking Deque first element: " +
LBD.getFirst());
}
} |
Output:
Exception in thread "main" java.util.NoSuchElementException at java.util.concurrent.LinkedBlockingDeque.getFirst(LinkedBlockingDeque.java:553) at GFG.main(GFG.java:28)
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#getFirst()