java.lang.NullPointerException
        at org.netbeans.api.java.source.ElementUtilities.isSynthetic(ElementUtilities.java:174)
        at org.netbeans.modules.refactoring.java.plugins.ChangeParamsTransformer.visitCompilationUnit(ChangeParamsTransformer.java:83)
        at org.netbeans.modules.refactoring.java.plugins.ChangeParamsTransformer.visitCompilationUnit(ChangeParamsTransformer.java:70)
        at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:482)
        at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:67)
        at org.netbeans.modules.refactoring.java.spi.JavaRefactoringPlugin$TransformTask.run(JavaRefactoringPlugin.java:363)
        at org.netbeans.modules.refactoring.java.spi.JavaRefactoringPlugin$TransformTask.run(JavaRefactoringPlugin.java:333)
        at org.netbeans.api.java.source.JavaSource$1.run(JavaSource.java:647)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:129)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:113)
        at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:189)
        at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:99)
        at org.netbeans.api.java.source.JavaSource.runModificationTask(JavaSource.java:663)
        at org.netbeans.modules.refactoring.java.spi.JavaRefactoringPlugin.processFiles(JavaRefactoringPlugin.java:244)
        at org.netbeans.modules.refactoring.java.spi.JavaRefactoringPlugin.createAndAddElements(JavaRefactoringPlugin.java:254)
        at org.netbeans.modules.refactoring.java.spi.JavaRefactoringPlugin.createAndAddElements(JavaRefactoringPlugin.java:270)
        at org.netbeans.modules.refactoring.java.plugins.ChangeParametersPlugin.prepare(ChangeParametersPlugin.java:192)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare2(AbstractRefactoring.java:419)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare(AbstractRefactoring.java:403)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.prepare(AbstractRefactoring.java:214)
        at org.netbeans.modules.refactoring.spi.impl.ParametersPanel$Prepare.run(ParametersPanel.java:802)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:577)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1030)