DATACMNS-1432 - Added Streamable.toList() and ….toSet() for convenience.

src/main/java/org/springframework/data/util/Streamable.java

@@ -146,6 +146,26 @@ public interface Streamable<T> extends Iterable<T>, Supplier<Stream<T>> {
 		return Streamable.of(() -> Stream.concat(this.stream(), stream.get()));
 	}
 
+	/**
+	 * Creates a new, unmodifiable {@link List}.
+	 * 
+	 * @return will never be {@literal null}.
+	 * @since 2.2
+	 */
+	default List<T> toList() {
+		return stream().collect(StreamUtils.toUnmodifiableList());
+	}
+
+	/**
+	 * Creates a new, unmodifiable {@link Set}.
+	 * 
+	 * @return will never be {@literal null}.
+	 * @since 2.2
+	 */
+	default Set<T> toSet() {
+		return stream().collect(StreamUtils.toUnmodifiableSet());
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see java.util.function.Supplier#get()

src/test/java/org/springframework/data/util/StreamableUnitTests.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * 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://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 org.springframework.data.util;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for {@link Streamable}
+ * 
+ * @author Oliver Gierke
+ * @soundtrack The Intersphere - Antitype (The Grand Delusion)
+ */
+public class StreamableUnitTests {
+
+	@Test // DATACMNS-1432
+	public void collectsToCollections() {
+
+		Streamable<Integer> streamable = Streamable.of(() -> Stream.of(1, 2, 1));
+
+		assertThat(streamable.toList()).containsExactly(1, 2, 1);
+		assertThat(streamable.toSet()).containsExactlyInAnyOrder(1, 2);
+	}
+}