Using filter in streams

Question

String[] arr={"121","4545","45456464"};
Arrays.stream(arr).filter(s->s.length()>4).toArray(String[]::new);

Can someone tell me exactly what's happening with toArray(String[]::new) in above code snippet.

Answer 1

String[]::new is actually the same as size -> new String[size]. A new String[] is created with the same size as the number of elements after applying the filter to the Stream. See also the javadoc of Stream.toArray

Answer 2

The toArray is creating a String[] containing the result of the filter in your case all strings whose length is greater than 4. The filter returns a Stream and so you are converting it into an array.

To print the filtered result rather than storing it into an array

Arrays.stream(arr).filter(s -> s.length() > 4).forEach(System.out::println);