adding async stream example

javav2/example_code/s3/src/main/java/com/example/s3/S3AsyncStreamOps.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2011-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *    http://aws.amazon.com/apache2.0
+ *
+ * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
+ * OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.example.s3;
+
+import software.amazon.awssdk.async.AsyncResponseHandler;
+import software.amazon.awssdk.services.s3.S3AsyncClient;
+import software.amazon.awssdk.services.s3.model.GetObjectRequest;
+import software.amazon.awssdk.utils.FunctionalUtils;
+
+import java.nio.file.Paths;
+import java.util.concurrent.CompletableFuture;
+
+public class S3AsyncStreamOps {
+
+    private static final String BUCKET = "sample-bucket";
+	private static final String KEY = "testfile.out";
+
+	public static void main(String[] args) {
+    	S3AsyncClient client = S3AsyncClient.create();
+      final CompletableFuture<Void> futureGet = client.getObject(
+                GetObjectRequest.builder()
+                                .bucket(BUCKET)
+                                .key(KEY)
+                                .build(),
+                AsyncResponseHandler.toFile(Paths.get("myfile.out")));
+      futureGet.whenComplete((resp, err) -> {
+            try {
+                if (resp != null) {
+                    System.out.println(resp);
+                } else {
+                    // Handle error
+                    err.printStackTrace();
+                }
+            } finally {
+                // Lets the application shut down. Only close the client when you are completely done with it
+                FunctionalUtils.invokeSafely(client::close);
+            }
+        });
+    }
+}