How to convert List to int[] in Java? [duplicate]

Answer 1

With Eclipse Collections, you can do the following if you have a list of type java.util.List:

List integers = Lists.mutable.with(1, 2, 3, 4, 5);
int[] ints = LazyIterate.adapt(integers).collectInt(i -> i).toArray();

Assert.assertArrayEquals(new int[]{1, 2, 3, 4, 5}, ints);

If you already have an Eclipse Collections type like MutableList, you can do the following:

MutableList integers = Lists.mutable.with(1, 2, 3, 4, 5);
int[] ints = integers.asLazy().collectInt(i -> i).toArray();

Assert.assertArrayEquals(new int[]{1, 2, 3, 4, 5}, ints);

Note: I am a committer for Eclipse Collections