El método addFirst(E e) de BlockingDeque inserta el elemento pasado en el parámetro al frente de Deque si hay espacio. Si BlockingDeque tiene una capacidad restringida y no queda espacio para la inserción, devuelve una IllegalStateException .
Sintaxis:
public void addFirst(E e)
Parámetros: este método acepta un parámetro obligatorio e que es el elemento que se insertará al frente del BlockingDeque.
Devoluciones: Este método no devuelve nada.
Excepción:
- IllegalStateException : si el elemento no se puede agregar en este momento debido a restricciones de capacidad
- NullPointerException : si el elemento especificado es nulo
Nota : El método addFirst() de BlockingDeque se ha heredado de la clase LinkedBlockingDeque en Java.
Los siguientes programas ilustran el método addFirst() de BlockingQueue:
Programa 1:
// Java Program Demonstrate addFirst()
// method of BlockingDeque
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
// create object of BlockingDeque
BlockingDeque<Integer> BD
= new LinkedBlockingDeque<Integer>();
// Add numbers to front of BlockingDeque
BD.addFirst(7855642);
BD.addFirst(35658786);
BD.addFirst(5278367);
BD.addFirst(74381793);
// before removing print Dequq
System.out.println("Blocking Deque: " + BD);
}
}
Blocking Deque: [74381793, 5278367, 35658786, 7855642]
Programa 2:
// Java Program Demonstrate addFirst()
// method of BlockingDeque
// when it is Full
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
// create object of BlockingDeque
// size of list
BlockingDeque<Integer> BD
= new LinkedBlockingDeque<Integer>(3);
// Add numbers to front of BlockingDeque
BD.addFirst(7855642);
BD.addFirst(35658786);
BD.addFirst(5278367);
// it is full
BD.addFirst(74381793);
// before removing print Deque
System.out.println("Blocking Deque: " + BD);
}
}
Producción:
Exception in thread "main" java.lang.IllegalStateException: Deque full
at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:326)
at GFG.main(GFG.java:24)
Programa 3:
// Java Program Demonstrate addFirst()
// method of BlockingDeque
// when nill is inserted
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
// create object of BlockingDeque
BlockingDeque<Integer> BD
= new LinkedBlockingDeque<Integer>();
// Add numbers to front of BlockingDeque
BD.addFirst(7855642);
BD.addFirst(35658786);
BD.addFirst(5278367);
// NULL
BD.addFirst(null);
// before removing print Deque
System.out.println("Blocking Deque: " + BD);
}
}
Producción:
Exception in thread "main" java.lang.NullPointerException
at java.util.concurrent.LinkedBlockingDeque.offerFirst(LinkedBlockingDeque.java:342)
at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:325)
at GFG.main(GFG.java:24)
Referencia: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#addFirst(E)