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pmd-java/src/main/resources/category/java/bestpractices.xml

@@ -1442,15 +1442,52 @@ class Foo{
           class="net.sourceforge.pmd.lang.java.rule.bestpractices.UnnecessaryVarargsArrayCreationRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_java_bestpractices.html#unnecessaryvarargsarraycreation">
         <description>
-            todo
+            Reports explicit array creation when a varargs is expected.
+            For instance:
+            ```java
+            Arrays.asList(new String[] { "foo", "bar", });
+            ```
+            can be replaced by:
+            ```java
+            Arrays.asList("foo", "bar");
+            ```
+
+            This rule also reports such array creations when they are confusing, because the array is a subtype of the component type of the expected array type.
+            For instance if you have
+            ```java
+            void varargs(Object... parm);
+            ```
+            and call it like so
+            ```java
+            varargs(new String[]{"a"});
+            ```
+            it is not clear whether you intended the method to receive the value `new Object[]{ new String[] {"a"} }` or just `new String[] {"a"}` (the latter happens). This confusion occurs because `String[]` is both a subtype of `Object[]` and of `Object`. To clarify your intent in this case, use a cast or pass individual elements like so:
+            ```java
+            // varargs call
+            // parm will be `new Object[] { "a" }`
+            varargs("a");
+
+            // non-varargs call
+            // parm will be `new String[] { "a" }`
+            varargs((Object[]) new String[]{"a"});
+
+            // varargs call
+            // parm will be `new Object[] { new String[] { "a" } }`
+            varargs((Object) new String[]{"a"});
+            ```
         </description>
         <priority>3</priority>
         <example><![CDATA[
-            class C {
-                // todo
-            }
-            ]]>
-        </example>
+import java.util.Arrays;
+
+class C {
+    static {
+        Arrays.asList(new String[]{"foo", "bar",});
+        // should be
+        Arrays.asList("foo", "bar");
+    }
+}
+            ]]></example>
     </rule>