Family Day update

Task/100-doors/Java/100-doors-2.java

@@ -1,6 +1,14 @@
-class HundredDoors {
+import java.util.BitSet;
+
+public class HundredDoors {
     public static void main(String[] args) {
-        for (int i = 1; i <= 10; i++)
-            System.out.printf("Door %d is open.%n", i * i);
+        final int n = 100;
+        var a = new BitSet(n);
+        for (int i = 1; i <= n; i++) {
+            for (int j = i - 1; j < n; j += i) {
+                a.flip(j);
+            }
+        }
+        a.stream().map(i -> i + 1).forEachOrdered(System.out::println);
     }
 }