convert-array-to-list-and-list-to-array
Converting between an Array and a List in Java
1. Overview
This quick article is going to show how to convert between an Array and a List using core Java libraries, Guava or Apache Commons Collections.
This article is part of the “Java – Back to Basic” series here on Baeldung.
2. Convert List to Array
@Test
public void givenUsingCoreJava_whenListConvertedToArray_thenCorrect() {
List<Integer> sourceList = Arrays.asList(0, 1, 2, 3, 4, 5);
Integer[] targetArray = sourceList.toArray(new Integer[sourceList.size()]);
}
3. Convert Array to List
@Test
public void givenUsingCoreJava_whenArrayConvertedToList_thenCorrect() {
Integer[] sourceArray = { 0, 1, 2, 3, 4, 5 };
List<Integer> targetList = Arrays.asList(sourceArray);
}
Note that this is a fixed-sized list that will still be backed by the array. If you want a standard ArrayList you can simply instantiate one as so:
List<Integer> targetList = new ArrayList<Integer>(Arrays.asList(sourceArray));
3.2. Using Guava
@Test
public void givenUsingGuava_whenArrayConvertedToList_thenCorrect() {
Integer[] sourceArray = { 0, 1, 2, 3, 4, 5 };
List<Integer> targetList = Lists.newArrayList(sourceArray);
}
3.3. Using Commons Collections
And finally, let’s use the Apache Commons Collections – CollectionUtils.addAll API to fill in the elements of the array into an empty List:
@Test
public void givenUsingCommonsCollections_whenArrayConvertedToList_thenCorrect() {
Integer[] sourceArray = { 0, 1, 2, 3, 4, 5 };
List<Integer> targetList = new ArrayList<>(6);
CollectionUtils.addAll(targetList, sourceArray);
}
4. Conclusion
The implementation of all these examples and code snippets can be found over on GitHub – this is a Maven-based project, so it should be easy to import and run as it is.