DATACMNS-867 - Avoid allocations from Method.getParameterTypes() where possible.

We now prefer an explicit Method.getParameterCount() over accessing the parameter types array and its length to avoid the overhead of cloning the array.

Original pull request: #187.

src/test/java/org/springframework/data/mapping/model/ClassGeneratingPropertyAccessorFactoryTests.java

@@ -116,7 +116,7 @@ public class ClassGeneratingPropertyAccessorFactoryTests {
 
 		Constructor<?>[] declaredConstructors = persistentPropertyAccessor.getClass().getDeclaredConstructors();
 		assertThat(declaredConstructors.length).isEqualTo(1);
-		assertThat(declaredConstructors[0].getParameterTypes().length).isEqualTo(1);
+		assertThat(declaredConstructors[0].getParameterCount()).isEqualTo(1);
 		assertThat(declaredConstructors[0].getParameterTypes()[0]).isEqualTo(expectedConstructorType);
 	}