Método DelayQueue put() en Java con ejemplos

El método put(E ele) de la clase DelayQueue en Java se usa para insertar un elemento dado en el contenedor de la cola de retraso. Hetre, E es el tipo de elemento mantenido por este contenedor DelayQueue.
 

Sintaxis :  

public void put(E ele)

Parámetros: este método acepta solo un parámetro ele . Es el elemento que se insertará en la cola de retraso.
Valor de retorno: el tipo de retorno del método es nulo y no devuelve ningún valor.
Excepción: 
 

• NullPointerException : se lanza si el valor dado es nulo.

Los siguientes programas ilustran el método put() de DelayQueue en Java:
Programa 1 : 
 

// Java program to illustrate the put()
// method in Java
 
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
 
public class GFG {
    public static void main(String args[])
    {
        // Create DelayQueue instance
        DelayQueue<Delayed> queue = new DelayQueue<Delayed>();
 
        // Initially Delay Queue is empty
        System.out.println("Before calling put() : "
                           + queue.isEmpty());
 
        // Create an object of type Delayed
        Delayed ele = new Delayed() {
            public long getDelay(TimeUnit unit)
            {
                return 24; // some value is returned
            }
 
            public int compareTo(Delayed o)
            {
                if (o.getDelay(TimeUnit.DAYS) >
                              this.getDelay(TimeUnit.DAYS))
                    return 1;
                else if (o.getDelay(TimeUnit.DAYS) == 
                                this.getDelay(TimeUnit.DAYS))
                    return 0;
                return -1;
            }
        };
 
        // Insert the created object to DelayQueue
        // using the put() method
        queue.put(ele);
 
        // Check if DelayQueue is empty.
        System.out.println("After calling put() : "
                           + queue.isEmpty());
    }
}

Before calling put() : true
After calling put() : false

Programa 2 : Demostración de NullPointerException. 
 

// Java program to illustrate the Exception thrown
// by put() method of DelayQueue
 
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
 
public class GFG {
    public static void main(String args[])
    {
        DelayQueue<Delayed> queue = new DelayQueue<Delayed>();
 
        try {
            queue.put(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

java.lang.NullPointerException

Referencia : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/DelayQueue.html#put(E)