September 2017 Update

Task/100-doors/Java/100-doors-1.java

@@ -1 +1,17 @@
-N.println(IntStream.rangeClosed(1, 100).filter(i -> Math.pow((int) Math.sqrt(i), 2) == i).boxed().join(", ", "Open Doors: ", ""));
+class HundredDoors {
+    public static void main(String[] args) {
+        boolean[] doors = new boolean[101];
+
+        for (int i = 1; i < doors.length; i++) {
+            for (int j = i; j < doors.length; j += i) {
+                doors[j] = !doors[j];
+            }
+        }
+
+        for (int i = 1; i < doors.length; i++) {
+            if (doors[i]) {
+                System.out.printf("Door %d is open.%n", i);
+            }
+        }
+    }
+}