Fix ForLoopCanBeForeach flagging loops with two iterators

Resolves #784

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/bestpractices/ForLoopCanBeForeachRule.java

@@ -16,6 +16,7 @@ import net.sourceforge.pmd.lang.java.ast.ASTExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTForInit;
 import net.sourceforge.pmd.lang.java.ast.ASTForStatement;
 import net.sourceforge.pmd.lang.java.ast.ASTForUpdate;
+import net.sourceforge.pmd.lang.java.ast.ASTLocalVariableDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTName;
 import net.sourceforge.pmd.lang.java.ast.ASTPrimaryPrefix;
 import net.sourceforge.pmd.lang.java.ast.ASTPrimarySuffix;
@@ -102,12 +103,17 @@ public class ForLoopCanBeForeachRule extends AbstractJavaRule {
     }
 
 
-    /* Finds the declaration of the index variable and its occurrences */
+    /* Finds the declaration of the index variable and its occurrences, null to abort */
     private Entry<VariableNameDeclaration, List<NameOccurrence>> getIndexVarDeclaration(ASTForInit init, ASTForUpdate update) {
         if (init == null) {
             return guessIndexVarFromUpdate(update);
         }
 
+        int numDeclaredVars = init.getFirstChildOfType(ASTLocalVariableDeclaration.class).findChildrenOfType(ASTVariableDeclarator.class).size();
+        if (numDeclaredVars > 1) {
+            return null; // will abort in the calling function
+        }
+
         Map<VariableNameDeclaration, List<NameOccurrence>> decls = init.getScope().getDeclarations(VariableNameDeclaration.class);
         Entry<VariableNameDeclaration, List<NameOccurrence>> indexVarAndOccurrences = null;
 

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/bestpractices/xml/ForLoopCanBeForeach.xml

@@ -287,4 +287,25 @@
         }
         ]]></code>
     </test-code>
+
+    <test-code>
+        <description>Iterating on multiple iterators should whitelist the loop, refs #784
+        </description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+        class Foo {
+          void loop() {
+            Iterable<E> it;
+            Iterable<E> other;
+            for (Iterator<E> iterator = it.iterator(), otherIterator = other.iterator(); iterator.hasNext();) {
+	            E item = iterator.next();
+	            E otherItem = otherIterator.next();
+	            doStuff();
+            }
+          }
+        }
+        ]]></code>
+    </test-code>
+
+
 </test-data>