How to transform String Array to int Array with streams

Question

I'm making a simple class that takes an array of Strings and returns an array of integers with the length of each string in them. I'm trying to use the Java 8 Stream API to do it.

public int[] findMostSimilar(String[] words) {

    return Arrays.stream(words).map(n -> n.length()).toArray();

}

But an error appears in the stream itself indicating

incompatible types, required: int[], found: java.lang.Object[].

Any ideas how to accomplish what I want?

Very similar/possible duplicate: Java stream toArray() convert to a specific type of array — GBlodgett
– GBlodgett, Commented Jan 16, 2019 at 21:26

Nicholas K · Accepted Answer · 2019-01-16 18:25:49Z

20

First lets see why your attempt didn't work :

Arrays.stream(words).map(n -> n.length()).toArray();

The above statement returns Object[]. You could use .toArray(Integer[]::new); but then this would return Integer[]

Instead you can make use of mapToInt :

int[] array = Arrays.stream(words).mapToInt(String::length).toArray();

edited Jan 16, 2019 at 18:25

answered Jan 16, 2019 at 18:10

Nicholas K

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pvpkiran · Accepted Answer · 2019-01-16 18:12:48Z

1

This should work.

int[] ints = Arrays.stream(words).mapToInt(String::length).toArray();

answered Jan 16, 2019 at 18:12

pvpkiran

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