The reason why in main there is no need to call join, while in Junit you need...

The reason why in main there is no need to call join, while in Junit you need to call join to wait for the thread to finish

README.md

@@ -11,4 +11,4 @@
 
 *Useful Links*
 * [Java Concurrency](https://www.callicoder.com/java-concurrency-issues-and-thread-synchronization/)
-* Java 9 Concurrency Cookbook (2019).pdf (included)
+* Java 9 Concurrency Cookbook (2019).pdf *ch-02* (included)
\ No newline at end of file

src/test/java/TestMemoryConsistencyJunit.java

+/*
+In a Java program's `main` method, you typically don't need to use `join()` because the Java Virtual Machine (JVM) will not exit until all non-daemon threads have finished execution¹.
+This means that even if the `main` method finishes, the JVM will still wait for all spawned threads to complete before it exits¹.
+
+However, in a JUnit test, the situation is different. The JUnit framework itself is running in the main thread, and it executes each test method (each marked with `@Test`) in turn¹. If a test method spawns a new thread and then returns, JUnit will consider that test method as finished and proceed to the next test¹.
+It won't wait for the spawned thread to finish¹. This can lead to unpredictable and incorrect results, because the test might finish before the thread has completed its work¹.
+
+Therefore, in a JUnit test, if you spawn a thread and you want to wait for that thread to finish before proceeding
+(for example, to check the results of the thread's work), you would use `join()`¹.
+ This causes the current thread (the main JUnit thread) to pause and wait for the spawned thread to finish¹.
+
+Source: Conversation with Bing, 11/15/2023
+(1) java - Why can classes being unit tested with JUnit not have a main .... https://stackoverflow.com/questions/4365883/why-can-classes-being-unit-tested-with-junit-not-have-a-main.
+(2) java junit has no main function - Stack Overflow. https://stackoverflow.com/questions/14011981/java-junit-has-no-main-function.
+(3) java - Testing main method by junit - Stack Overflow. https://stackoverflow.com/questions/36349827/testing-main-method-by-junit.
+(4) How do you unit test main method in Java? - Stack Overflow. https://stackoverflow.com/questions/59855313/how-do-you-unit-test-main-method-in-java.*/
+
+import junit.framework.TestCase;
+
+public class TestMemoryConsistencyJunit extends TestCase {
+
+    volatile boolean sayHello= false;
+
+    public void testMemoryInconsistent() throws InterruptedException {
+
+        Thread thread = new Thread(() -> {
+            while (!sayHello) {
+            }
+
+            System.out.println("Hello World!");
+
+            while (sayHello) {
+            }
+
+            System.out.println("Good Bye!");
+        });
+
+        thread.start();
+
+        Thread.sleep(1000);
+        System.out.println("Say Hello..");
+        sayHello = true;
+
+        Thread.sleep(1000);
+        System.out.println("Say Bye..");
+        sayHello = false;
+    }
+}
+