Fixed warnings

Author: padilo

spring-context/src/test/java/org/springframework/cache/CacheRxJavaTests.java

@@ -30,8 +30,6 @@
 import rx.Single;
 import rx.observers.TestSubscriber;
 
-import java.util.List;
-
 import static org.junit.Assert.*;
 
 /**
@@ -148,9 +146,7 @@ public Single<Object> nullValue() {
 		@Cacheable("throwable")
 		@Override
 		public Single<Object> throwable() {
-			return Single.fromCallable(() -> {
-                throw new RuntimeException();
-            });
+			return Single.error(new RuntimeException());
 		}
 
 		@Cacheable("neverFinish")

spring-context/src/test/java/org/springframework/cache/ReactorTests.java

@@ -86,6 +86,7 @@ public void nullValue() {
 
 		// Mono values cannot be null
 		testSubscriber.assertError();
+		assertNull("Shouldn't be cached", cache.get(SimpleKey.EMPTY));
 	}
 
 	@Test
@@ -167,9 +168,7 @@ public Mono<Object> nullValue() {
 		@Cacheable("throwable")
 		@Override
 		public Mono<Object> throwable() {
-			return Mono.fromCallable(() -> {
-				throw new RuntimeException();
-			});
+			return Mono.error(new RuntimeException());
 		}
 
 		@Cacheable("neverFinish")