fixed violations for PMD rule UseCollectionIsEmpty. Issue #744

config/pmd.xml

@@ -121,7 +121,6 @@
     <exclude name="UncommentedEmptyMethod"/>
     <!-- till #996 -->
     <exclude name="PreserveStackTrace"/>
-    <exclude name="UseCollectionIsEmpty"/>
     <exclude name="EmptyMethodInAbstractClassShouldBeAbstract"/>
     <exclude name="SingularField"/>
     <exclude name="TooFewBranchesForASwitchStatement"/>

src/main/java/com/puppycrawl/tools/checkstyle/checks/coding/VariableDeclarationUsageDistanceCheck.java

@@ -487,7 +487,7 @@ public class VariableDeclarationUsageDistanceCheck extends Check
                     }
                     // If expression doesn't contain variable and this variable
                     // hasn't been met yet, than distance + 1.
-                    else if (variableUsageExpressions.size() == 0
+                    else if (variableUsageExpressions.isEmpty()
                             && currentStatementAst.getType() != TokenTypes.VARIABLE_DEF)
                     {
                         dist++;