Java Collections - ArrayList.toArray() Examples

Java Collections Java Java API 

Class:

java.util.ArrayList

Methods:

public Object[] toArray()

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

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

Returns an array containing all of the elements in this list in proper sequence (from first to last element); 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. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)

Examples

Example of: toArray()

package com.logicbig.example.arraylist;

import java.util.*;

public class ToArrayExample {

    public static void main(String... args) {
        // Convert to Object array
        ArrayList<String> list = new ArrayList<>(Arrays.asList("One", "Two", "Three"));
        Object[] array = list.toArray();
        System.out.println("Array length: " + array.length);
        System.out.println("First element: " + array[0]);
    }
}

Output

Array length: 3
First element: One

JDK 25

Example of: toArray(T[] a)

package com.logicbig.example.arraylist;

import java.util.*;

public class ToArrayExample2 {

    public static void main(String... args) {
        // Convert to typed array
        ArrayList<String> list = new ArrayList<>(Arrays.asList("A", "B", "C"));
        String[] stringArray = list.toArray(new String[0]);
        System.out.println("String array: " + Arrays.toString(stringArray));
    }
}

Output

String array: [A, B, C]

JDK 25