Add CompletableFutureUtils

Convenience util for CompletableFuture.allOf method

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

@@ -0,0 +1,37 @@
+package bisq.common.util;/*
+ * 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/>.
+ */
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.stream.Collectors;
+
+public class CompletableFutureUtils {
+    /**
+     * @param list List of futures
+     * @param <T>  The generic type of the future
+     * @return Returns a CompletableFuture with a list of the futures we got as parameter once all futures
+     * are completed (incl. exceptionally completed).
+     */
+    public static <T> CompletableFuture<List<T>> allOf(List<CompletableFuture<T>> list) {
+        CompletableFuture<Void> allFuturesResult = CompletableFuture.allOf(list.toArray(new CompletableFuture[list.size()]));
+        return allFuturesResult.thenApply(v ->
+                list.stream().
+                        map(CompletableFuture::join).
+                        collect(Collectors.<T>toList())
+        );
+    }
+}