DelayQueue toArray() method in Java with Examples

The toArray() method of DelayQueue is used to return an array containing all the elements in DelayQueue. There elements are not in any specific order in the array.

Syntax:

public Object[] toArray ()
           or
public T[] toArray (T[] a)

Parameters: This method either accepts no parameters or it takes an array T[] a as parameter which is the array into which the elements of the list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Return Value: The function returns an array containing all the elements in this list.

Exception: The first overload of this method throws no exceptions. However, the second overload throws following exceptions:



  • ArrayStoreException: if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue.
  • NullPointerException: if the specified array is null.

Below programs illustrate the DelayQueue.toArray() method:

Program 1:

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// Java Program Demonstrate DelayQueue toArray() method
  
import java.util.concurrent.*;
import java.util.*;
  
// The DelayObject for DelayQueue
// It must implement Delayed and
// its getDelay() and compareTo() method
class DelayObject implements Delayed {
  
    private String name;
    private long time;
  
    // Contructor of DelayObject
    public DelayObject(String name, long delayTime)
    {
        this.name = name;
        this.time = System.currentTimeMillis()
                    + delayTime;
    }
  
    // Implementing getDelay() method of Delayed
    @Override
    public long getDelay(TimeUnit unit)
    {
        long diff = time - System.currentTimeMillis();
        return unit.convert(diff, TimeUnit.MILLISECONDS);
    }
  
    // Implementing compareTo() method of Delayed
    @Override
    public int compareTo(Delayed obj)
    {
        if (this.time < ((DelayObject)obj).time) {
            return -1;
        }
        if (this.time > ((DelayObject)obj).time) {
            return 1;
        }
        return 0;
    }
  
    // Implementing toString() method of Delayed
    @Override
    public String toString()
    {
        return "\n{"
            + " " + name + ", time=" + time + "}";
    }
}
  
// Driver Class
public class GFG {
    public static void main(String[] args) throws InterruptedException
    {
  
        // create object of DelayQueue
        // using DelayQueue() constructor
        BlockingQueue<DelayObject> DQ
            = new DelayQueue<DelayObject>();
  
        // Add numbers to end of DelayQueue
        // using add() method
        DQ.add(new DelayObject("A", 1));
        DQ.add(new DelayObject("B", 2));
        DQ.add(new DelayObject("C", 3));
        DQ.add(new DelayObject("D", 4));
  
        // print queue
        System.out.println("DelayQueue: "
                           + DQ);
  
        // Get the array of the elements
        // of the ArrayList
        // using toArray() method
        Object[] arr = DQ.toArray();
  
        // print the array elements
        System.out.println("Elements of DelayQueue"
                           + " as Array: "
                           + Arrays.toString(arr));
    }
}

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Output:

DelayQueue: [
{ A, time=1546842694862}, 
{ B, time=1546842694863}, 
{ C, time=1546842694864}, 
{ D, time=1546842694865}]
Elements of DelayQueue as Array: [
{ A, time=1546842694862}, 
{ B, time=1546842694863}, 
{ C, time=1546842694864}, 
{ D, time=1546842694865}]

Program 2:

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// Java Program Demonstrate DelayQueue toArray() method
  
import java.util.concurrent.*;
import java.util.*;
  
// The DelayObject for DelayQueue
// It must implement Delayed and
// its getDelay() and compareTo() method
class DelayObject implements Delayed {
  
    private String name;
    private long time;
  
    // Contructor of DelayObject
    public DelayObject(String name, long delayTime)
    {
        this.name = name;
        this.time = System.currentTimeMillis()
                    + delayTime;
    }
  
    // Implementing getDelay() method of Delayed
    @Override
    public long getDelay(TimeUnit unit)
    {
        long diff = time - System.currentTimeMillis();
        return unit.convert(diff, TimeUnit.MILLISECONDS);
    }
  
    // Implementing compareTo() method of Delayed
    @Override
    public int compareTo(Delayed obj)
    {
        if (this.time < ((DelayObject)obj).time) {
            return -1;
        }
        if (this.time > ((DelayObject)obj).time) {
            return 1;
        }
        return 0;
    }
  
    // Implementing toString() method of Delayed
    @Override
    public String toString()
    {
        return "\n{"
            + " " + name + ", time=" + time + "}";
    }
}
  
// Driver Class
public class GFG {
    public static void main(String[] args) throws InterruptedException
    {
  
        // create object of DelayQueue
        // using DelayQueue() constructor
        BlockingQueue<DelayObject> DQ
            = new DelayQueue<DelayObject>();
  
        // Add numbers to end of DelayQueue
        // using add() method
        DQ.add(new DelayObject("A", 1));
        DQ.add(new DelayObject("B", 2));
        DQ.add(new DelayObject("C", 3));
        DQ.add(new DelayObject("D", 4));
  
        // print queue
        System.out.println("DelayQueue: "
                           + DQ);
  
        // Get the array of the elements
        // of the DelayQueue
        // using toArray(T[]) method
        Delayed arr[] = new Delayed[DQ.size()];
        arr = DQ.toArray(arr);
  
        // print the array elements
        System.out.println("Elements of ArrayList"
                           + " as Array: "
                           + Arrays.toString(arr));
    }
}

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Output:

DelayQueue: [
{ A, time=1546842699503}, 
{ B, time=1546842699504}, 
{ C, time=1546842699505}, 
{ D, time=1546842699506}]
Elements of ArrayList as Array: [
{ A, time=1546842699503}, 
{ B, time=1546842699504}, 
{ C, time=1546842699505}, 
{ D, time=1546842699506}]


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