Java.util.ArrayList.toArray(T[]) Method

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Description

The java.util.ArrayList.toArray(T[]) method returns an array containing all of the elements in this list in proper sequence (from first to last element).Following are the important points about ArrayList.toArray() −

• The runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.

• If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the collection is set to null.

Declaration

Following is the declaration for java.util.ArrayList.toArray() method

public <T> T[] toArray(T[] a)

Parameters

a − This 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

This method returns an array containing the elements of the list.

Exception

• ArrayStoreException − If the runtime type of the specified array is not a supertype of the runtime type of every element in this list.

• NullPointerException − If the specified array is null.

Example

The following example shows the usage of java.util.Arraylist.toArray() method.

package com.tutorialspoint;

import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String[] args) {
      
      // create an empty array list with an initial capacity
      ArrayList<Integer> arrlist = new ArrayList<Integer>();

      // use add() method to add values in the list
      arrlist.add(10);
      arrlist.add(12);
      arrlist.add(31);
      arrlist.add(49);
      
      System.out.println("Printing elements of array1");

      // let us print all the elements available in list
      for (Integer number : arrlist) {
         System.out.println("Number = " + number);
      }  

      // toArray copies content into other array
      Integer list2[] = new Integer[arrlist.size()];
      list2 = arrlist.toArray(list2);

      System.out.println("Printing elements of array2");

      // let us print all the elements available in list
      for (Integer number : list2) {
         System.out.println("Number = " + number);
      }
   }
} 

Let us compile and run the above program, this will produce the following result −

Printing elements of array1
Number = 10
Number = 12
Number = 31
Number = 49
Printing elements of array2
Number = 10
Number = 12
Number = 31
Number = 49