Add CompletableFutureUtil

Signed-off-by: HenrikJannsen <boilingfrog@gmx.com>

common/src/main/java/bisq/common/util/CompletableFutureUtil.java

@@ -0,0 +1,57 @@
+/*
+ * This file is part of Bisq.
+ *
+ * Bisq is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * Bisq is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Bisq. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package bisq.common.util;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+//todo
+public class CompletableFutureUtil {
+    public static <T> CompletableFuture<List<T>> allOf(Collection<CompletableFuture<T>> collection) {
+        //noinspection unchecked
+        return allOf(collection.toArray(new CompletableFuture[0]));
+    }
+
+    public static <T> CompletableFuture<List<T>> allOf(Stream<CompletableFuture<T>> stream) {
+        return allOf(stream.collect(Collectors.toList()));
+    }
+
+    public static <T> CompletableFuture<List<T>> allOf(CompletableFuture<T>... list) {
+        CompletableFuture<List<T>> result = CompletableFuture.allOf(list).thenApply(v ->
+                Stream.of(list)
+                        .map(future -> {
+                            // We want to return the results in list, not the futures. Once allOf call is complete
+                            // we know that all futures have completed (normally, exceptional or cancelled).
+                            // For exceptional and canceled cases we throw an exception.
+                            T res = future.join();
+                            if (future.isCompletedExceptionally()) {
+                                throw new RuntimeException((future.handle((r, throwable) -> throwable).join()));
+                            }
+                            if (future.isCancelled()) {
+                                throw new RuntimeException("Future got canceled");
+                            }
+                            return res;
+                        })
+                        .collect(Collectors.<T>toList())
+        );
+        return result;
+    }
+}