This bug was originally marked as duplicate of bug 219404, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE Dev (Build 201210210002)
VM: Java HotSpot(TM) 64-Bit Server VM, 23.5-b02, Java(TM) SE Runtime Environment, 1.7.0_09-b05
OS: Windows 7

User Comments:
javydreamercsw: Trying to refactor.

ecerichter: Trying to encapsulate fields. Reproducible always, even on 201210210002.
What I've typed:

1) Shift+Ctrl+E over variable name (to open "Encapsulate Fields" dialog).
2) Hit "Enter" over the name. It doesn't confirm the window (as it did in the past)
3) Hit "Ctrl+Enter" to confirme de window.

Error is thrown.

ecerichter: Encapsulating fields.
Cursor was on attribute name. I've hit "Enter".
Cursor moved to selection box for getter.
I've hit "Ctrl+Enter" in order to confirm the generation, without changing anything from defaults.

salaboy: Refactoring -> encapulating fields




Stacktrace: 
java.lang.NullPointerException
   at org.netbeans.modules.refactoring.java.plugins.EncapsulateFieldRefactoringPlugin.getRelevantFiles(EncapsulateFieldRefactoringPlugin.java:507)
   at org.netbeans.modules.refactoring.java.plugins.EncapsulateFieldRefactoringPlugin.prepareEncapsulator(EncapsulateFieldRefactoringPlugin.java:472)
   at org.netbeans.modules.refactoring.java.plugins.EncapsulateFieldsPlugin.prepare(EncapsulateFieldsPlugin.java:198)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare2(AbstractRefactoring.java:437)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare(AbstractRefactoring.java:421)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.prepare(AbstractRefactoring.java:232)