ArrayDeque.toArray(E[]) in Java

ArrayDeque.toArray(E[]): This method is available in java.util.ArrayDeque class of Java.

Syntax:

<E> E[] java.util.ArrayDeque.toArray(E[] a)

This method takes one argument. This method returns an array containing all of the elements in this deque in proper sequence.

Parameters: One parameter is required for this method.

a: the array into which the elements of the deque are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Returns: an array containing all of the elements in this deque.

Throws:

1. ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque.

2. NullPointerException - if the specified array is null

Approach 1: When no exception

Java

import java.util.ArrayDeque;
import java.util.Arrays;

public class ArrayDequetoArray2 {
    public static void main(String[] args) {

        ArrayDeque<Integer> arrayDeque =
                     new ArrayDeque<Integer>();

        arrayDeque.add(1);
        arrayDeque.add(4);
        arrayDeque.add(7781);
        arrayDeque.add(478);
        arrayDeque.add(118);
        arrayDeque.add(99);
        Integer list2[] = new Integer[5];
        list2 = arrayDeque.toArray(list2);
        System.out.println(Arrays.toString(list2));

    }
}

Output:

[1, 4, 7781, 478, 118, 99]

Approach 2: ArrayStoreException 

Java

import java.util.ArrayDeque;
import java.util.Arrays;

public class ArrayDequetoArray2 {
    public static void main(String[] args) {

        ArrayDeque<Integer> arrayDeque = 
                           new ArrayDeque<Integer>();

        arrayDeque.add(1);
        arrayDeque.add(4);
        arrayDeque.add(7781);
        arrayDeque.add(478);
        arrayDeque.add(118);
        arrayDeque.add(99);
        Long list2[] = new Long[5];
        list2 = arrayDeque.toArray(list2);
        System.out.println(Arrays.toString(list2));

    }
}

Output:

Exception in thread "main" java.lang.ArrayStoreException: arraycopy: element type mismatch: can not cast one of the elements of java.lang.Object[] to the type of the destination array, java.lang.Long
	at java.base/java.lang.System.arraycopy(Native Method)
	at java.base/java.util.Arrays.copyOfRange(Arrays.java:3786)
	at java.base/java.util.ArrayDeque.toArray(ArrayDeque.java:1079)
	at java.base/java.util.ArrayDeque.toArray(ArrayDeque.java:1130)

Approach 3: NullPointerException 

Java

import java.util.ArrayDeque;
import java.util.Arrays;

public class ArrayDequetoArray2 {
    public static void main(String[] args) {

        ArrayDeque<Integer> arrayDeque = null;

        Integer list2[] = new Integer[5];
        list2 = arrayDeque.toArray(list2);
        System.out.println(Arrays.toString(list2));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.ArrayDeque.toArray(Object[])" because "arrayDeque" is null