The signature data file for "javax.swing" package is not longer generated due to the fix of Sigtest issue #17 "If setup command failed inconsistent signature file can be written". See https://sigtest.dev.java.net/issues/show_bug.cgi?id=17

The Signature setup command produces the following output and nothing is written to sigfile:
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*Package: javax.swing*
Constant checking: on
Found in total: 17325 classes
Hidden class found: javax.swing.text.ParagraphView$Row in method protected void
javax.swing.text.ParagraphView.adjustRow(javax.swing.text.ParagraphView$Row,int,int) in
class javax.swing.text.ParagraphView
Hidden class found: javax.swing.tree.PathPlaceHolder in method protected void
javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(java.util.Vector<javax.swing.tree.PathPlaceHolder>,javax.swing.tree.TreePath)
in class javax.swing.JTree$EmptySelectionModel
Hidden class found: javax.swing.text.ParagraphView$Row in method protected void
javax.swing.text.ParagraphView.adjustRow(javax.swing.text.ParagraphView$Row,int,int) in
class javax.swing.text.html.ParagraphView
Hidden class found: javax.swing.tree.PathPlaceHolder in method protected void
javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(java.util.Vector<javax.swing.tree.PathPlaceHolder>,javax.swing.tree.TreePath)
in class javax.swing.tree.DefaultTreeSelectionModel
Selected by -Package: 1818 classes
Written to sigfile: 543 classes(and 375 inner classes)
STATUS:Failed.4 errors
======

This happens because the Sun's JRE contains two methods that use package-private class as a parameter. See corresponding bugs:
   6387360 Usage of package-private class as a parameter of a method (javax.swing.text.ParagraphView)
   6387579 Usage of package-private class as parameter of a method (javax.swing.tree.DefaultTreeSelectionModel)

Note that it was decided to keep these methods in the JRE as it is without correction. So it's necessary to have a way to generate the JRE signatures in such case.