Sync with underscore-java.

Author: javadev

src/main/java/com/github/underscore/Underscore.java

@@ -2182,7 +2182,7 @@ public T get() {
      * Documented, #wrap
      */
     public static <T> Function<Void, T> wrap(
-            final Function<T, T> function, final Function<Function<T, T>, T> wrapper) {
+            final UnaryOperator<T> function, final Function<UnaryOperator<T>, T> wrapper) {
         return arg -> wrapper.apply(function);
     }
 
@@ -3914,7 +3914,7 @@ private static List<Map.Entry<String, Integer>> getEntries(
 
     public static class ValueThenKeyComparator<
                     K extends Comparable<? super K>, V extends Comparable<? super V>>
-            implements Comparator<Map.Entry<K, V>> {
+            implements Comparator<Map.Entry<K, V>>, java.io.Serializable {
 
         public int compare(Map.Entry<K, V> a, Map.Entry<K, V> b) {
             int cmp1 = b.getValue().compareTo(a.getValue());

src/test/java/com/github/underscore/FunctionsTest.java

@@ -37,6 +37,8 @@
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
+
 import org.junit.jupiter.api.Test;
 
 /**
@@ -250,7 +252,7 @@ void once() {
     */
     @Test
     void wrap() {
-        Function<String, String> hello = name -> "hello: " + name;
+        UnaryOperator<String> hello = name -> "hello: " + name;
         Function<Void, String> result =
                 Underscore.wrap(hello, func -> "before, " + func.apply("moe") + ", after");
         assertEquals("before, hello: moe, after", result.apply(null));