added Backpressure

src/main/java/com/nisum/backpressureStrategy/BackpressureSubscriber.java

+package com.nisum.backpressureStrategy;
+
+import java.util.concurrent.Flow;
+
+public class BackpressureSubscriber<Integer> implements Flow.Subscriber<Integer>{
+
+    private Flow.Subscription subscription;
+    @Override
+    public void onSubscribe(Flow.Subscription subscription) {
+        System.out.println("Subscribed");
+        this.subscription = subscription;
+        subscription.request(1);
+    }
+
+    @Override
+    public void onNext(Integer item) {
+        System.out.println(Thread.currentThread().getName() + " | Received = " + item);
+        try {
+            Thread.sleep(1000);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        subscription.request(1);
+    }
+
+    @Override
+    public void onError(Throwable throwable) {
+        System.out.println(Thread.currentThread().getName() + " | ERROR = "
+                + throwable.getClass().getSimpleName() + " | " + throwable.getMessage());
+    }
+
+    @Override
+    public void onComplete() {
+        System.out.println("Completed");
+    }
+}

src/main/java/com/nisum/backpressureStrategy/BackpressureUsingBufferStrategy.java

+package com.nisum.backpressureStrategy;
+
+import java.util.concurrent.Flow;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.SubmissionPublisher;
+
+public class BackpressureUsingBufferStrategy {
+    public static void main(String[] args) throws InterruptedException {
+
+        final int BUFFER = 4;
+        Flow.Publisher<Integer> backPressurePublisher = new SubmissionPublisher<>(ForkJoinPool.commonPool(), BUFFER);
+        BackpressureSubscriber<Integer> backpressureSubscriber = new BackpressureSubscriber<>();
+        backPressurePublisher.subscribe(backpressureSubscriber);
+
+
+        for (int i = 0; i < 10; i++) {
+            System.out.println(Thread.currentThread().getName() + " Publishing = " + i);
+            ((SubmissionPublisher<Integer>) backPressurePublisher).submit(i);
+
+        }
+
+        ((SubmissionPublisher<Integer>) backPressurePublisher).close();
+        Thread.sleep(10000);
+    }
+}