What is the equivalent lambda expression for System.out::println
I stumbled upon the following Java code which is using a method reference for System.out.println
:
class SomeClass {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1,2,3,4,5,6,7,8,9);
numbers.forEach(System.out::println);
}
}
}
What is the equivalent lambda expression for System.out::println
?
The method reference System.out::println
will evaluate System.out
first, then create the equivalent of a lambda expression which captures the evaluated value. Usually, you would useo -> System.out.println(o)
to achieve the same as the method reference, but this lambda expression will evaluate System.out
each time the method will be called.
So an exact equivalent would be:
PrintStream p = Objects.requireNonNull(System.out);
numbers.forEach(o -> p.println(o));
which will make a difference if someone invokes System.setOut(…);
in-between.
It's :
numbers.forEach(i -> {System.out.println(i);});
or even simpler :
numbers.forEach(i -> System.out.println(i));