Move CompletableFuture examples
This commit is contained in:
Grzegorz Piwowarek
@@ -14,7 +14,6 @@
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- [Convert String to int or Integer in Java](http://www.baeldung.com/java-convert-string-to-int-or-integer)
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- [Convert char to String in Java](http://www.baeldung.com/java-convert-char-to-string)
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- [Guide to Java 8’s Functional Interfaces](http://www.baeldung.com/java-8-functional-interfaces)
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- [Guide To CompletableFuture](http://www.baeldung.com/java-completablefuture)
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- [Introduction to Thread Pools in Java](http://www.baeldung.com/thread-pool-java-and-guava)
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- [Guide to Java 8 Collectors](http://www.baeldung.com/java-8-collectors)
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- [The Java 8 Stream API Tutorial](http://www.baeldung.com/java-8-streams)
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@@ -1,209 +0,0 @@
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package com.baeldung.completablefuture;
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import java.util.concurrent.*;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import org.junit.Test;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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public class CompletableFutureTest {
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@Test
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public void whenRunningCompletableFutureAsynchronously_thenGetMethodWaitsForResult() throws InterruptedException, ExecutionException {
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Future<String> completableFuture = calculateAsync();
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String result = completableFuture.get();
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assertEquals("Hello", result);
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}
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public Future<String> calculateAsync() throws InterruptedException {
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CompletableFuture<String> completableFuture = new CompletableFuture<>();
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Executors.newCachedThreadPool().submit(() -> {
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Thread.sleep(500);
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completableFuture.complete("Hello");
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return null;
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});
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return completableFuture;
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}
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@Test
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public void whenRunningCompletableFutureWithResult_thenGetMethodReturnsImmediately() throws InterruptedException, ExecutionException {
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Future<String> completableFuture = CompletableFuture.completedFuture("Hello");
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String result = completableFuture.get();
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assertEquals("Hello", result);
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}
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public Future<String> calculateAsyncWithCancellation() throws InterruptedException {
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CompletableFuture<String> completableFuture = new CompletableFuture<>();
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Executors.newCachedThreadPool().submit(() -> {
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Thread.sleep(500);
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completableFuture.cancel(false);
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return null;
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});
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return completableFuture;
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}
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@Test(expected = CancellationException.class)
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public void whenCancelingTheFuture_thenThrowsCancellationException() throws ExecutionException, InterruptedException {
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Future<String> future = calculateAsyncWithCancellation();
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future.get();
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}
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@Test
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public void whenCreatingCompletableFutureWithSupplyAsync_thenFutureReturnsValue() throws ExecutionException, InterruptedException {
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CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello");
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assertEquals("Hello", future.get());
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}
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@Test
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public void whenAddingThenAcceptToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
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CompletableFuture<Void> future = completableFuture.thenAccept(s -> System.out.println("Computation returned: " + s));
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future.get();
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}
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@Test
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public void whenAddingThenRunToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
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CompletableFuture<Void> future = completableFuture.thenRun(() -> System.out.println("Computation finished."));
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future.get();
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}
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@Test
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public void whenAddingThenApplyToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
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CompletableFuture<String> future = completableFuture.thenApply(s -> s + " World");
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assertEquals("Hello World", future.get());
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}
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@Test
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public void whenUsingThenCompose_thenFuturesExecuteSequentially() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
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.thenCompose(s -> CompletableFuture.supplyAsync(() -> s + " World"));
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assertEquals("Hello World", completableFuture.get());
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}
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@Test
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public void whenUsingThenCombine_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
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.thenCombine(CompletableFuture.supplyAsync(() -> " World"),
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(s1, s2) -> s1 + s2);
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assertEquals("Hello World", completableFuture.get());
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}
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@Test
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public void whenUsingThenAcceptBoth_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
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CompletableFuture.supplyAsync(() -> "Hello")
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.thenAcceptBoth(CompletableFuture.supplyAsync(() -> " World"),
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(s1, s2) -> System.out.println(s1 + s2));
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}
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@Test
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public void whenFutureCombinedWithAllOfCompletes_thenAllFuturesAreDone() throws ExecutionException, InterruptedException {
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CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> "Hello");
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CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> "Beautiful");
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CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> "World");
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CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(future1, future2, future3);
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// ...
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combinedFuture.get();
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assertTrue(future1.isDone());
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assertTrue(future2.isDone());
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assertTrue(future3.isDone());
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String combined = Stream.of(future1, future2, future3)
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.map(CompletableFuture::join)
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.collect(Collectors.joining(" "));
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assertEquals("Hello Beautiful World", combined);
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}
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@Test
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public void whenFutureThrows_thenHandleMethodReceivesException() throws ExecutionException, InterruptedException {
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String name = null;
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// ...
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {
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if (name == null) {
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throw new RuntimeException("Computation error!");
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}
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return "Hello, " + name;
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}).handle((s, t) -> s != null ? s : "Hello, Stranger!");
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assertEquals("Hello, Stranger!", completableFuture.get());
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}
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@Test(expected = ExecutionException.class)
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public void whenCompletingFutureExceptionally_thenGetMethodThrows() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = new CompletableFuture<>();
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// ...
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completableFuture.completeExceptionally(new RuntimeException("Calculation failed!"));
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// ...
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completableFuture.get();
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}
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@Test
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public void whenAddingThenApplyAsyncToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
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CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
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CompletableFuture<String> future = completableFuture.thenApplyAsync(s -> s + " World");
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assertEquals("Hello World", future.get());
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}
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}
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