BAEL-8021-Guide-to-CompletableFuture-join-vs-get (#16800)

* BAEL-8021-Guide-to-CompletableFuture-join-vs-get

* BAEL-8021-Guide-to-CompletableFuture-join-vs-get

* BAEL-8021-Guide-to-CompletableFuture-join-vs-get

* BAEL-8021-Guide-to-CompletableFuture-join-vs-get

---------

Co-authored-by: tienvn <[email protected]>

Author: vunamtien

core-java-modules/core-java-concurrency-advanced-5/src/test/java/com/baeldung/joinvsget/CompletableFutureUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.joinvsget;
+
+import org.junit.jupiter.api.Test;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.ExecutionException;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class CompletableFutureUnitTest {
+
+    @Test
+    public void givenJoinMethod_whenThrow_thenGetUncheckedException() {
+        CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Test join");
+        
+        assertEquals("Test join", future.join());
+
+        CompletableFuture<String> exceptionFuture = CompletableFuture.failedFuture(new RuntimeException("Test join exception"));
+
+        assertThrows(CompletionException.class, exceptionFuture::join);
+    }
+
+    @Test
+    public void givenGetMethod_whenThrow_thenGetCheckedException() {
+        CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Test get");
+
+        try {
+            assertEquals("Test get", future.get());
+        } catch (InterruptedException | ExecutionException e) {
+            fail("Exception should not be thrown");
+        }
+
+        CompletableFuture<String> exceptionFuture = CompletableFuture.failedFuture(new RuntimeException("Test get exception"));
+
+        assertThrows(ExecutionException.class, exceptionFuture::get);
+    }
+}