JAVA-11499 move rxjava* modules to new rxjava-modules (#12342)

* JAVA-11499 move rxjava* modules to new rxjava-modules

* JAVA-11499 addressed PR comments

rxjava-modules/rxjava-libraries/src/main/java/com/baeldung/rxjava/RandomRelay.java

@@ -0,0 +1,32 @@
+package com.baeldung.rxjava;
+
+import com.jakewharton.rxrelay2.Relay;
+import io.reactivex.Observer;
+import io.reactivex.disposables.Disposables;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+public class RandomRelay extends Relay<Integer> {
+    Random random = new Random();
+
+    List<Observer<? super Integer>> observers = new ArrayList<>();
+
+    @Override
+    public void accept(Integer integer) {
+        int observerIndex = random.nextInt(observers.size()) & Integer.MAX_VALUE;
+        observers.get(observerIndex).onNext(integer);
+    }
+
+    @Override
+    public boolean hasObservers() {
+        return observers.isEmpty();
+    }
+
+    @Override
+    protected void subscribeActual(Observer<? super Integer> observer) {
+        observers.add(observer);
+        observer.onSubscribe(Disposables.fromRunnable(() -> System.out.println("Disposed")));
+    }
+}