Initial data commit

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

@@ -0,0 +1,17 @@
+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);
+            }
+        }
+    }
+}

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

@@ -0,0 +1,14 @@
+import java.util.BitSet;
+
+public class HundredDoors {
+    public static void main(String[] args) {
+        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);
+    }
+}

Task/100-doors/Java/100-doors-3.java

@@ -0,0 +1,6 @@
+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);
+    }
+}

Task/100-doors/Java/100-doors-4.java

@@ -0,0 +1,12 @@
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+class HundredDoors {
+    public static void main(String args[]) {
+        String openDoors = IntStream.rangeClosed(1, 100)
+                .filter(i -> Math.pow((int) Math.sqrt(i), 2) == i)
+                .mapToObj(Integer::toString)
+                .collect(Collectors.joining(", "));
+        System.out.printf("Open doors: %s%n", openDoors);
+    }
+}