How to increment a "number" in a Java 8 lambda expression in a loop?

You can use a static variable :

public class Poubelle {

    private static int position = 1;

    public static void setPosition (List<PersonMatchInfo> listPersonMatchInfo) {

          listPersonMatchInfo.forEach(pmi -> {
          pmi.setPosition(position++);
        });
    }
}

You can use AtomicInteger, and incrementAndGet method on it.

Other solution would be int[] position = new int[]{1};

and incrementing position[0]++;