Make CompositeFileComparator.toString() simpler

Add test

Author: garydgregory

src/main/java/org/apache/commons/io/comparator/CompositeFileComparator.java

@@ -18,6 +18,7 @@
 
 import java.io.File;
 import java.io.Serializable;
+import java.util.Arrays;
 import java.util.Comparator;
 import java.util.function.IntFunction;
 import java.util.stream.Stream;
@@ -97,16 +98,8 @@ private Comparator<File>[] emptyArray() {
      */
     @Override
     public String toString() {
-        final StringBuilder builder = new StringBuilder();
-        builder.append(super.toString());
-        builder.append('{');
-        for (int i = 0; i < delegates.length; i++) {
-            if (i > 0) {
-                builder.append(',');
-            }
-            builder.append(delegates[i]);
-        }
-        builder.append('}');
+        final StringBuilder builder = new StringBuilder(super.toString());
+        builder.append(Arrays.toString(delegates));
         return builder.toString();
     }
 }

src/test/java/org/apache/commons/io/comparator/CompositeFileComparatorTest.java

@@ -115,4 +115,15 @@ void testConstructorIterable_order() {
         assertTrue(c.compare(lessFile, moreFile) < 0, "less");
         assertTrue(c.compare(moreFile, lessFile) > 0, "more");
     }
+
+    @Test
+    void testToString() {
+        final List<Comparator<File>> list = new ArrayList<>();
+        list.add(SizeFileComparator.SIZE_COMPARATOR);
+        list.add(ExtensionFileComparator.EXTENSION_COMPARATOR);
+        final Comparator<File> c = new CompositeFileComparator(list);
+        final String string = c.toString();
+        assertTrue(string.contains("SizeFileComparator"));
+        assertTrue(string.contains("ExtensionFileComparator"));
+    }
 }