Java ConcurrentLinkedQueue toArray() Method

The toArray() method of ConcurrentLinkedQueue class returns an array containing all the elements present in the queue in no particular order.

Syntax:

1.	public Object[] toArray()
2.	public<T> T[]toArray(T[] a)

Parameters:

NA
a ? this is the array in which the elements of the queue will be stored.

Type Parameters:

T ? this is the component type of the array to hold the collection.

Specified By:

The toArray() method of ConcurrentLinkedQueue class is specified by :

toArray() method in interface Collection<E>.

Override:

The toArray() method of ConcurrentLinkedQueue class is overridden by :

toArray() method in class AbstractCollection<E>.

Return Value:

The toArray() method returns an array that contains all the elements of this queue.

Throws:

The toArray() method throws NullPointerException if the specified array is null.

Example 1

import java.util.concurrent.ConcurrentLinkedQueue;
public class ConcurrentLinkedQueueToArrayExample1 {
    static  int j=1;
    public static void main(String[] args) {
        ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue();
        queue.add("Reema");
        queue.add("Rahul");
        queue.add("Rita");
        queue.add("Ramesh");
        Object[] a=queue.toArray();
        for(int i=0 ;i<a.length;i++){
            System.out.println("Element  "+ j++ +": "+ a[i]);
        }
    }
}

Test it Now

Output:

Element  1: Reema
Element  2: Rahul
Element  3: Rita
Element  4: Ramesh

Example 2

import java.util.concurrent.ConcurrentLinkedQueue;
public class ConcurrentLinkedQueueToArrayExample2 {
    public static void main(String[] args) {
        ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue();
        queue.add(8);
        queue.add(5);
        queue.add(17);
        queue.add(80);
        queue.add(2);
        Object[] a = queue.toArray();
        System.out.print("Elements : ");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
        System.out.println();
        System.out.print("Ascending order : ");
        for (int i = 0; i < a.length; i++) {
            for (int j = i + 1; j < a.length; j++) {
                Object temp = 0;
               if (a[i] > a[j]) {
                    temp = a[i];
                    a[i] = a[j];
                    a[j] = temp;
               }
            }
        }
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }

    }
}

Test it Now

Output:

Error:(22, 25) java: bad operand types for binary operator '>'
  first type:  java.lang.Object
  second type: java.lang.Object

Operator '<' cannot be applied to java.lang.Object. If we do so, it will give you an error.

This example is the solution to the above described program.

Example 3

import java.util.concurrent.ConcurrentLinkedQueue;
public class ConcurrentLinkedQueueToArrayExample3 {
    public static void main(String[] args) {
        ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue();
        queue.add(8);
        queue.add(5);
        queue.add(17);
        queue.add(80);
        queue.add(2);
        Integer[] a = new Integer[5];
        Integer[] b = queue.toArray(a);
        System.out.print("Elements : ");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+" ");
        }
        System.out.println();
        System.out.print("Ascending order : ");
        for (int i = 0; i < b.length; i++) {
            for (int j = i + 1; j < b.length; j++) {
                int temp = 0;
                if (a[i] > a[j]) {
                    temp = b[i];
                    b[i] = b[j];
                    b[j] = temp;
                }
            }
        }
        for (int i = 0; i < b.length; i++) {
            System.out.print(b[i] + " ");
        }
        System.out.print("\nDecending order : ");
        for (int i = 4; i >=0; i--) {
            System.out.print(b[i] + " ");
        }
    }
}

Test it Now

Output:

Elements : 8 5 17 80 2 
Ascending order : 2 5 8 17 80 
Decending order : 80 17 8 5 2

Example 4

import java.util.concurrent.ConcurrentLinkedQueue;
public class ConcurrentLinkedQueueToArrayExample4 {
    public static void main(String[] args) {
        ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue();
        queue.add("Reema");
        queue.add("Rahul");
        queue.add("Rita");
        queue.add("Ramesh");
        Object[] a=queue.toArray(null);
        for(int i=0 ;i<a.length;i++){
            System.out.println("Element : "+a[i]);
        }
    }
}

Test it Now

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.util.concurrent.ConcurrentLinkedQueue.toArray(ConcurrentLinkedQueue.java:638)
	at com.javaTpoint.ConcurrentLinkedQueueToArrayExample4.main(ConcurrentLinkedQueueToArrayExample4.java:11)

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