Java stream toArray() convert to a specific type of array

by

Use toArray(size -> new String[size]) or toArray(String[]::new).

String[] strings = Arrays.stream(line.split(",")).map(String::trim).toArray(String[]::new);

This is actually a lambda expression for 

.toArray(new IntFunction<String[]>() {
        @Override
        public String[] apply(int size) {
            return new String[size];
        }
    });

Where you are telling convert the array to a String array of same size.

From the docs

The generator function takes an integer, which is the size of the desired array, and produces an array of the desired size. This can be concisely expressed with an array constructor reference:

 Person[] men = people.stream()
                      .filter(p -> p.getGender() == MALE)
                      .toArray(Person[]::new);

Type Parameters:

A – the element type of the resulting array

Parameters:

generator – a function which produces a new array of the desired type and the provided length

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