Java tutorial
import java.util.HashMap; import java.util.Map; public class Main { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); for (int i = 0; i < 10; i++) { map.putIfAbsent(i, "val" + i); } map.forEach((id, val) -> System.out.println(val)); System.out.println(map.getOrDefault(42, "not found")); // not found } }