【stream_reduce】import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) {
List<Integer> l = getDatas();
System.out.println(
l.stream().map((a) -> (a.toString()))
.reduce((a, b) -> (a + b ))
.orElse("ko"));
}
public static List<Integer> getDatas() {
List<Integer> l = new ArrayList(100);
for (int i = 0; i < 99; i++) {
l.add(i);
}
return l;
}
}
