pmd: fix #977 MisplacedNullCheck makes false positives

pmd/etc/changelog.txt

@@ -1,5 +1,6 @@
 ????? ??, 2013 - 5.0.3:
 
+Fixed bug  977: MisplacedNullCheck makes false positives
 Fixed bug  984: Cyclomatic complexity should treat constructors like methods
 Fixed bug  985: Suppressed methods shouldn't affect avg CyclomaticComplexity
 Fixed bug  992: Class java.beans.Statement triggered in CloseResource rule

pmd/src/main/resources/rulesets/java/basic.xml

@@ -386,13 +386,21 @@ Either the check is useless (the variable will never be "null") or it is incorre
     <![CDATA[
 //Expression
     /*[self::ConditionalOrExpression or self::ConditionalAndExpression]
-     /descendant::PrimaryExpression/PrimaryPrefix
-      /Name[starts-with(@Image,
-      concat(ancestor::PrimaryExpression/following-sibling::EqualityExpression
-       [./PrimaryExpression/PrimaryPrefix/Literal/NullLiteral]
-     /PrimaryExpression/PrimaryPrefix
-      /Name[count(../../PrimarySuffix)=0]/@Image,"."))
-    ]
+    /descendant::PrimaryExpression/PrimaryPrefix
+    /Name[starts-with(@Image,
+        concat(ancestor::PrimaryExpression/following-sibling::EqualityExpression
+            [./PrimaryExpression/PrimaryPrefix/Literal/NullLiteral]
+            /PrimaryExpression/PrimaryPrefix
+            /Name[count(../../PrimarySuffix)=0]/@Image,".")
+        )
+     ]
+     [count(ancestor::ConditionalAndExpression/EqualityExpression
+            [@Image='!=']
+            [./PrimaryExpression/PrimaryPrefix/Literal/NullLiteral]
+            [starts-with(following-sibling::*/PrimaryExpression/PrimaryPrefix/Name/@Image,
+                concat(./PrimaryExpression/PrimaryPrefix/Name/@Image, '.'))]
+      ) = 0
+     ]
     ]]>
         </value>
         </property>

pmd/src/test/resources/net/sourceforge/pmd/lang/java/rule/basic/xml/MisplacedNullCheck.xml

@@ -69,4 +69,17 @@ public class Foo {
 }
         ]]></code>
     </test-code>
+    <test-code>
+        <description>#977 MisplacedNullCheck makes false positives</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+public class Test {
+    public void method(final String value,final String oldValue) {
+        if ((value != null && !value.equals(oldValue)) || value == null) {
+            // Do something
+        }
+    }
+}
+]]></code>
+    </test-code>
 </test-data>