Migrate toward java.util.function

- Package-private changes only
- Maintains binary and source compatibility

src/main/java/org/apache/commons/collections4/functors/ChainedTransformer.java

@@ -108,7 +108,7 @@ public class ChainedTransformer<T> implements Transformer<T, T>, Serializable {
      * @since 3.1
      */
     public Transformer<? super T, ? extends T>[] getTransformers() {
-        return FunctorUtils.<T, T>copy(iTransformers);
+        return FunctorUtils.copy(iTransformers);
     }
 
     /**

src/main/java/org/apache/commons/collections4/functors/FunctorUtils.java

@@ -111,17 +111,17 @@ final class FunctorUtils {
     }
 
     /**
-     * Copy method
+     * Copy method.
      *
      * @param transformers  the transformers to copy
      * @return a clone of the transformers
      */
     @SuppressWarnings("unchecked")
-    static <I, O> Transformer<I, O>[] copy(final Transformer<? super I, ? extends O>... transformers) {
+    static <T extends Function<?, ?>> T[] copy(final T... transformers) {
         if (transformers == null) {
             return null;
         }
-        return (Transformer<I, O>[]) transformers.clone();
+        return transformers.clone();
     }
 
     /**

src/main/java/org/apache/commons/collections4/functors/SwitchTransformer.java

@@ -174,7 +174,7 @@ public class SwitchTransformer<I, O> implements Transformer<I, O>, Serializable
      * @since 3.1
      */
     public Transformer<? super I, ? extends O>[] getTransformers() {
-        return FunctorUtils.<I, O>copy(iTransformers);
+        return FunctorUtils.copy(iTransformers);
     }
 
     /**