Java map an array of Strings to an array of Integers

Question

I found this code on SO to map strings to ints

Arrays.stream(myarray).mapToInt(Integer::parseInt).toArray();

But how do I make it map to Integer type not the primitive int?

I tried switching from Integer.parseInt to Integer.valueOf, but it seems that the mapToInt() method forces the primitive type.

I have an ArrayList of arrays of Integers, so I cannot use primitive ints.

The Integer class is the same thing as an int really. It wraps and unwraps an int for you, so, hypothetically, they are the same — Josh Heaps
– Josh Heaps, Commented May 9, 2017 at 18:27
Yes, but this method shows an error "The method add(Integer[]) in the type ArrayList<Integer[]> is not applicable for the arguments (int[])" when I try to append the mapped array to my ArrayList of Integers. — Fiodor
– Fiodor, Commented May 9, 2017 at 18:30

Flown · Accepted Answer · 2017-05-09 18:47:18Z

29

Since String and Integer are both reference types you can simply call Stream::map to transform your array.

Integer[] boxed = Stream.of(myarray).map(Integer::valueOf).toArray(Integer[]::new);

answered May 9, 2017 at 18:47

Flown

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Ousmane D. · Accepted Answer · 2017-05-10 10:08:15Z

5

you can use the Stream<Integer> boxed() method.

Stream<Integer> boxed() returns a Stream consisting of the elements of this stream, each boxed to an Integer.

ArrayList<Integer[]> resultSet = new ArrayList<>();
resultSet.add(Arrays.stream(myarray).mapToInt(Integer::parseInt).boxed().toArray(Integer[]::new));

edited May 10, 2017 at 10:08

answered May 9, 2017 at 18:34

Ousmane D.

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2 Comments

Fiodor Over a year ago

Thanks a lot. Is there a way to do it more elegantly, though? Like for example in JavaScript myarray.map(function(e) {return parseInt(e);});? It seems like a lot of nested calls and intermediate types for just a simple String[] to Integer[] conversion.

Teena George Over a year ago

You can map instead of boxing and mapInt: String [] myArray = {"1", "2", "3", "4"};

Integer[] integerList =Arrays.stream(myArray).map(Integer::valueOf).toArray(Integer[]::new);    System.out.print(integerList[0].getClass()); //output: class java.lang.Integer

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