[BAEL-6486] - Returning a Value After Finishing Thread's Job in Java (#14101)
* feat: threads with return value * pmd violation
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lucaCambi77
GitHub
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package com.baeldung.concurrent.threadreturnvalue.task;
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import java.math.BigInteger;
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public class FactorialCalculator {
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public static BigInteger factorial(BigInteger end) {
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BigInteger start = BigInteger.ONE;
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BigInteger res = BigInteger.ONE;
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for (int i = start.add(BigInteger.ONE)
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.intValue(); i <= end.intValue(); i++) {
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res = res.multiply(BigInteger.valueOf(i));
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}
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return res;
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}
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public static BigInteger factorial(BigInteger start, BigInteger end) {
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BigInteger res = start;
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for (int i = start.add(BigInteger.ONE)
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.intValue(); i <= end.intValue(); i++) {
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res = res.multiply(BigInteger.valueOf(i));
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}
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return res;
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.task.callable;
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import java.math.BigInteger;
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import java.util.List;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Executors;
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import java.util.concurrent.Future;
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public class CallableExecutor {
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public BigInteger execute(List<CallableFactorialTask> tasks) {
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BigInteger result = BigInteger.ZERO;
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ExecutorService cachedPool = Executors.newCachedThreadPool();
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List<Future<BigInteger>> futures;
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try {
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futures = cachedPool.invokeAll(tasks);
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} catch (InterruptedException e) {
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// exception handling example
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throw new RuntimeException(e);
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}
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for (Future<BigInteger> future : futures) {
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try {
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result = result.add(future.get());
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} catch (InterruptedException | ExecutionException e) {
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// exception handling example
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throw new RuntimeException(e);
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}
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}
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return result;
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.task.callable;
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import static com.baeldung.concurrent.threadreturnvalue.task.FactorialCalculator.factorial;
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import java.math.BigInteger;
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import java.util.concurrent.Callable;
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public class CallableFactorialTask implements Callable<BigInteger> {
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private final Integer value;
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public CallableFactorialTask(int value) {
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this.value = value;
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}
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@Override
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public BigInteger call() {
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return factorial(BigInteger.valueOf(value));
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.task.fork;
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import java.math.BigInteger;
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import java.util.List;
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import java.util.concurrent.Callable;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.ForkJoinPool;
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import java.util.concurrent.Future;
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public class ForkExecutor {
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private final ForkJoinPool forkJoinPool = ForkJoinPool.commonPool();
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public BigInteger execute(ForkFactorialTask forkFactorial) {
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return forkJoinPool.invoke(forkFactorial);
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}
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public BigInteger execute(List<Callable<BigInteger>> forkFactorials) {
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List<Future<BigInteger>> futures = forkJoinPool.invokeAll(forkFactorials);
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BigInteger result = BigInteger.ZERO;
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for (Future<BigInteger> future : futures) {
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try {
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result = result.add(future.get());
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} catch (InterruptedException | ExecutionException e) {
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// exception handling example
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throw new RuntimeException(e);
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}
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}
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return result;
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.task.fork;
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import static com.baeldung.concurrent.threadreturnvalue.task.FactorialCalculator.factorial;
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import java.math.BigInteger;
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import java.util.concurrent.RecursiveTask;
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public class ForkFactorialTask extends RecursiveTask<BigInteger> {
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private final int start;
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private final int end;
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private final int threshold;
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public ForkFactorialTask(int end, int threshold) {
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this.start = 1;
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this.end = end;
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this.threshold = threshold;
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}
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public ForkFactorialTask(int start, int end, int threshold) {
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this.start = start;
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this.end = end;
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this.threshold = threshold;
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}
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@Override
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protected BigInteger compute() {
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BigInteger sum = BigInteger.ONE;
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if (end - start > threshold) {
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int middle = (end + start) / 2;
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return sum.multiply(new ForkFactorialTask(start, middle, threshold).fork()
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.join()
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.multiply(new ForkFactorialTask(middle + 1, end, threshold).fork()
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.join()));
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}
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return sum.multiply(factorial(BigInteger.valueOf(start), BigInteger.valueOf(end)));
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.callable;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.math.BigInteger;
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import java.util.Arrays;
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import org.junit.jupiter.api.Test;
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import com.baeldung.concurrent.threadreturnvalue.task.callable.CallableExecutor;
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import com.baeldung.concurrent.threadreturnvalue.task.callable.CallableFactorialTask;
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public class CallableUnitTest {
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private final CallableExecutor callableExecutor = new CallableExecutor();
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@Test
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void givenCallableExecutor_whenExecuteFactorial_thenResultOk() {
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BigInteger result = callableExecutor.execute(Arrays.asList(new CallableFactorialTask(5), new CallableFactorialTask(3)));
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assertEquals(BigInteger.valueOf(126), result);
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.completableFuture;
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import static com.baeldung.concurrent.threadreturnvalue.task.FactorialCalculator.factorial;
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import static java.util.concurrent.CompletableFuture.allOf;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.math.BigInteger;
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import java.util.concurrent.CompletableFuture;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Executors;
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import org.junit.jupiter.api.Test;
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public class CompletableFutureUnitTest {
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@Test
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void givenCompletableFuture_whenSupplyAsyncFactorial_thenResultOk() throws ExecutionException, InterruptedException {
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CompletableFuture<BigInteger> completableFuture = CompletableFuture.supplyAsync(() -> factorial(BigInteger.valueOf(10)));
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assertEquals(BigInteger.valueOf(3628800), completableFuture.get());
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}
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@Test
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void givenCompletableFuture_whenComposeTasks_thenResultOk() throws ExecutionException, InterruptedException {
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CompletableFuture<BigInteger> completableFuture = CompletableFuture.supplyAsync(() -> factorial(BigInteger.valueOf(3)))
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.thenCompose(inputFromFirstTask -> CompletableFuture.supplyAsync(() -> factorial(inputFromFirstTask)));
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assertEquals(BigInteger.valueOf(720), completableFuture.get());
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}
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@Test
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void givenCompletableFuture_whenAllOfTasks_thenResultOk() {
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CompletableFuture<BigInteger> asyncTask1 = CompletableFuture.supplyAsync(() -> BigInteger.valueOf(5));
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CompletableFuture<String> asyncTask2 = CompletableFuture.supplyAsync(() -> "3");
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BigInteger result = allOf(asyncTask1, asyncTask2).thenApplyAsync(fn -> factorial(asyncTask1.join()).add(factorial(new BigInteger(asyncTask2.join()))), Executors.newFixedThreadPool(1))
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.join();
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assertEquals(BigInteger.valueOf(126), result);
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}
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}
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package com.baeldung.concurrent.threadreturnvalue.fork;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.math.BigInteger;
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import java.util.Arrays;
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import org.junit.jupiter.api.Test;
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import com.baeldung.concurrent.threadreturnvalue.task.callable.CallableFactorialTask;
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import com.baeldung.concurrent.threadreturnvalue.task.fork.ForkExecutor;
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import com.baeldung.concurrent.threadreturnvalue.task.fork.ForkFactorialTask;
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public class ForkUnitTest {
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private final ForkExecutor forkExecutor = new ForkExecutor();
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@Test
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void givenForkExecutor_whenExecuteRecursiveTask_thenResultOk() {
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assertEquals(BigInteger.valueOf(3628800), forkExecutor.execute(new ForkFactorialTask(10, 5)));
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}
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@Test
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void givenForkExecutor_whenExecuteCallable_thenResultOk() {
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assertEquals(BigInteger.valueOf(126), forkExecutor.execute(Arrays.asList(new CallableFactorialTask(5), new CallableFactorialTask(3))));
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}
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}
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