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Added test for the Guide to CompletableFuture (#611)

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Sergey Petunin 2016-08-16 03:16:19 +06:00 committed by Grzegorz Piwowarek
parent 2f331cecf8
commit 5195a4310e
1 changed files with 196 additions and 0 deletions
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core-java-8/src/test/java/com/baeldung/completablefuture/CompletableFutureTest.java Normal file
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package com.baeldung.completablefuture;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
public class CompletableFutureTest {
@Test
public void whenRunningCompletableFutureAsyncronously_thenGetMethodWaitsForResult() throws InterruptedException, ExecutionException {
Future<String> completableFuture = calculateAsync();
String result = completableFuture.get();
assertEquals("Hello", result);
}
public Future<String> calculateAsync() throws InterruptedException {
CompletableFuture<String> completableFuture = new CompletableFuture<>();
Executors.newCachedThreadPool().submit(() -> {
Thread.sleep(500);
completableFuture.complete("Hello");
return null;
});
return completableFuture;
}
@Test
public void whenRunningCompletableFutureWithResult_thenGetMethodReturnsImmediately() throws InterruptedException, ExecutionException {
Future<String> completableFuture = CompletableFuture.completedFuture("Hello");
String result = completableFuture.get();
assertEquals("Hello", result);
}
@Test
public void whenCreatingCompletableFutureWithSupplyAsync_thenFutureReturnsValue() throws ExecutionException, InterruptedException {
CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello");
assertEquals("Hello", future.get());
}
@Test
public void whenAddingThenAcceptToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<Void> future = completableFuture.thenAccept(s -> System.out.println("Computation returned: " + s));
future.get();
}
@Test
public void whenAddingThenRunToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<Void> future = completableFuture.thenRun(() -> System.out.println("Computation finished."));
future.get();
}
@Test
public void whenAddingThenApplyToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<String> future = completableFuture.thenApply(s -> s + " World");
assertEquals("Hello World", future.get());
}
@Test
public void whenUsingThenCompose_thenFuturesExecuteSequentially() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
.thenCompose(s -> CompletableFuture.supplyAsync(() -> s + " World"));
assertEquals("Hello World", completableFuture.get());
}
@Test
public void whenUsingThenCombine_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
.thenCombine(CompletableFuture.supplyAsync(() -> " World"),
(s1, s2) -> s1 + s2);
assertEquals("Hello World", completableFuture.get());
}
@Test
public void whenUsingThenAcceptBoth_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
CompletableFuture.supplyAsync(() -> "Hello")
.thenAcceptBoth(CompletableFuture.supplyAsync(() -> " World"),
(s1, s2) -> System.out.println(s1 + s2));
}
@Test
public void whenFutureCombinedWithAllOfCompletes_thenAllFuturesAreDone() throws ExecutionException, InterruptedException {
CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> "Beautiful");
CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> "World");
CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(future1, future2, future3);
// ...
combinedFuture.get();
assertTrue(future1.isDone());
assertTrue(future2.isDone());
assertTrue(future3.isDone());
String combined = Stream.of(future1, future2, future3)
.map(CompletableFuture::join)
.collect(Collectors.joining(" "));
assertEquals("Hello Beautiful World", combined);
}
@Test
public void whenFutureThrows_thenHandleMethodRecievesException() throws ExecutionException, InterruptedException {
String name = null;
// ...
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {
if (name == null) {
throw new RuntimeException("Computation error!");
}
return "Hello, " + name;
}).handle((s, t) -> {
if (s != null) {
return s;
} else {
return "Hello, Stranger!";
}
});
assertEquals("Hello, Stranger!", completableFuture.get());
}
@Test(expected = ExecutionException.class)
public void whenCompletingFutureExceptionally_thenGetMethodThrows() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = new CompletableFuture<>();
// ...
completableFuture.completeExceptionally(new RuntimeException("Calculation failed!"));
// ...
completableFuture.get();
}
@Test
public void whenAddingThenApplyAsyncToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<String> future = completableFuture.thenApplyAsync(s -> s + " World");
assertEquals("Hello World", future.get());
}
}