Bael 845 transfer queue (#1697)

* BAEL-845 tranferqueue article

* BAEL-845 m to m example

* BAEL-845 move code to test

* BAEL-845 use tryTransfer

* BAEL-845 proper if logic

* BAEL-845 proper test

* BAEL-845 robust test

core-java/src/main/java/com/baeldung/transferqueue/Consumer.java

@@ -1,11 +1,13 @@
 package com.baeldung.transferqueue;
 
 import java.util.concurrent.TransferQueue;
+import java.util.concurrent.atomic.AtomicInteger;
 
 public class Consumer implements Runnable {
     private final TransferQueue<String> transferQueue;
     private final String name;
     private final int numberOfMessagesToConsume;
+    public final AtomicInteger numberOfConsumedMessages = new AtomicInteger();
 
     public Consumer(TransferQueue<String> transferQueue, String name, int numberOfMessagesToConsume) {
         this.transferQueue = transferQueue;
@@ -28,6 +30,7 @@ public class Consumer implements Runnable {
     }
 
     private void longProcessing(String element) throws InterruptedException {
-        Thread.sleep(1_000);
+        numberOfConsumedMessages.incrementAndGet();
+        Thread.sleep(500);
     }
 }

core-java/src/main/java/com/baeldung/transferqueue/Producer.java

@@ -2,11 +2,13 @@ package com.baeldung.transferqueue;
 
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TransferQueue;
+import java.util.concurrent.atomic.AtomicInteger;
 
 public class Producer implements Runnable {
     private final TransferQueue<String> transferQueue;
     private final String name;
     private final Integer numberOfMessagesToProduce;
+    public final AtomicInteger numberOfProducedMessages = new AtomicInteger();
 
     public Producer(TransferQueue<String> transferQueue, String name, Integer numberOfMessagesToProduce) {
         this.transferQueue = transferQueue;
@@ -23,6 +25,7 @@ public class Producer implements Runnable {
                 if (!added) {
                     System.out.println("can not add an element due to the timeout");
                 } else {
+                    numberOfProducedMessages.incrementAndGet();
                     System.out.println("Producer: " + name + " transferred element: A" + i);
                 }
             } catch (InterruptedException e) {

core-java/src/test/java/com/baeldung/transferqueue/TransferQueueTest.java

@@ -1,9 +1,14 @@
 package com.baeldung.transferqueue;
 
+import org.junit.FixMethodOrder;
 import org.junit.Test;
+import org.junit.runners.MethodSorters;
 
 import java.util.concurrent.*;
 
+import static junit.framework.TestCase.assertEquals;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
 public class TransferQueueTest {
 
     @Test
@@ -25,6 +30,9 @@ public class TransferQueueTest {
         //then
         exService.awaitTermination(10_000, TimeUnit.MILLISECONDS);
         exService.shutdown();
+
+        assertEquals(producer1.numberOfProducedMessages.intValue(), 3);
+        assertEquals(producer2.numberOfProducedMessages.intValue(), 3);
     }
 
     @Test
@@ -42,6 +50,9 @@ public class TransferQueueTest {
         //then
         exService.awaitTermination(5000, TimeUnit.MILLISECONDS);
         exService.shutdown();
+
+        assertEquals(producer.numberOfProducedMessages.intValue(), 3);
+        assertEquals(consumer.numberOfConsumedMessages.intValue(), 3);
     }
 
     @Test
@@ -57,6 +68,7 @@ public class TransferQueueTest {
         //then
         exService.awaitTermination(5000, TimeUnit.MILLISECONDS);
         exService.shutdown();
-    }
 
+        assertEquals(producer.numberOfProducedMessages.intValue(), 0);
+    }
 }