StringUtils.join(Iterator, String) should only return null when the

Iterator is null

src/changes/changes.xml

@@ -90,6 +90,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action                   type="fix" dev="ggregory" due-to="guicaiyue">Javadoc: StringUtils.repeat("", "x", 3) = "xx"; #918.</action>
     <action                   type="fix" dev="ggregory" due-to="Marc Wrobel">Fix typos #920, #923.</action>
     <action                   type="fix" dev="ggregory" due-to="Bhimantoro Suryo Admodjo">Simplify condition #925.</action>
+    <action                   type="fix" dev="ggregory" due-to="Gary Gregory">StringUtils.join(Iterator, String) should only return null when the Iterator is null.</action>
     <!-- ADD -->
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add GitHub coverage.yml.</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add EnumUtils.getEnumSystemProperty(...).</action>
@@ -160,7 +161,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action issue="LANG-1662" type="add" dev="ggregory" due-to="Daniel Augusto Veronezi Salvador, Gary Gregory, Bruno P. Kinoshita">Let ReflectionToStringBuilder only reflect given field names #849.</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add Streams.of(Enumeration&lt;E&gt;).</action>
     <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add Streams.of(Iterable&lt;E&gt;).</action>
-    <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add LangCollectors.</action>
+    <action                   type="add" dev="ggregory" due-to="Gary Gregory">Add Streams.of(Iterator&lt;E&gt;).</action>
     <!-- UPDATE -->
     <action                   type="update" dev="ggregory" due-to="Dependabot, XenoAmess, Gary Gregory">Bump actions/cache from 2.1.4 to 3.0.7 #742, #752, #764, #833, #867.</action>
     <action                   type="update" dev="ggregory" due-to="Dependabot">Bump actions/checkout from 2 to 3 #819, #825, #859.</action>

src/main/java/org/apache/commons/lang3/StringUtils.java

@@ -4350,10 +4350,7 @@ public static String join(final int[] array, final char delimiter, final int sta
      * @since 2.3
      */
     public static String join(final Iterable<?> iterable, final char separator) {
-        if (iterable == null) {
+        return iterable != null ? join(iterable.iterator(), separator) : null;
-            return null;
-        }
-        return join(iterable.iterator(), separator);
     }
 
     /**
@@ -4371,10 +4368,7 @@ public static String join(final Iterable<?> iterable, final char separator) {
      * @since 2.3
      */
     public static String join(final Iterable<?> iterable, final String separator) {
-        if (iterable == null) {
+        return iterable != null ? join(iterable.iterator(), separator) : null;
-            return null;
-        }
-        return join(iterable.iterator(), separator);
     }
 
     /**
@@ -4436,7 +4430,6 @@ public static String join(final Iterator<?> iterator, final char separator) {
      * @return the joined String, {@code null} if null iterator input
      */
     public static String join(final Iterator<?> iterator, final String separator) {
-
         // handle null, zero and one elements before building a buffer
         if (iterator == null) {
             return null;
@@ -4444,25 +4437,18 @@ public static String join(final Iterator<?> iterator, final String separator) {
         if (!iterator.hasNext()) {
             return EMPTY;
         }
-        final Object first = iterator.next();
-        if (!iterator.hasNext()) {
-            return Objects.toString(first, "");
-        }
 
         // two or more elements
         final StringBuilder buf = new StringBuilder(STRING_BUILDER_SIZE); // Java default is 16, probably too small
-        if (first != null) {
-            buf.append(first);
-        }
 
         while (iterator.hasNext()) {
-            if (separator != null) {
-                buf.append(separator);
-            }
             final Object obj = iterator.next();
             if (obj != null) {
                 buf.append(obj);
             }
+            if (separator != null && iterator.hasNext()) {
+                buf.append(separator);
+            }
         }
         return buf.toString();
     }

src/test/java/org/apache/commons/lang3/StringUtilsTest.java

@@ -1310,7 +1310,7 @@ public void testJoin_IteratorString() {
 
         assertEquals(TEXT_LIST, StringUtils.join(Arrays.asList(ARRAY_LIST).iterator(), SEPARATOR));
 
-        assertNull(StringUtils.join(Arrays.asList(NULL_TO_STRING_LIST).iterator(), SEPARATOR));
+        assertEquals("null", StringUtils.join(Arrays.asList(NULL_TO_STRING_LIST).iterator(), SEPARATOR));
     }
 
     @Test