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The Java 8 Lambda way: ArrayList to an Array
15 July 2016

In an earlier post this year, 'Convert an ArrayList to an Array in Java', I commented on a way to convert an ArrayList to an Array in Java. Here is the example code from the earlier post.

List<String> results = new ArrayList<>();
...
results.toArray(new String[results.size()]);

This earlier way works fine, however it's old school. Here is the Java 8 Lambda way to convert an ArrayList to an Array:

Long[] longArray = longArrayList.stream()
    .map(Long::new)
    .toArray(Long[]::new);

This example works by mapping a new object for each item in the ArrayList's stream to the new stream, and then collecting that stream as an array.