Since JDK7b143 the following code throws GenericSignatureFormatError:

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    Class c = Class.forName("javax.swing.JComboBox$AccessibleJComboBox");
    System.out.println("Class = " + c);
    for ( Field f : c.getDeclaredFields()) {
        System.out.println(" [FIELD] " + f.getName());
        System.out.println(" [TYPE] " + f.getType());
        System.out.println(" [GENERICTYPE] " + f.getGenericType());
    }
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The output is:

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Class = class javax.swing.JComboBox$AccessibleJComboBox
 [FIELD] popupList
  [TYPE] class javax.swing.JList
  [GENERICTYPE] class javax.swing.JList
 [FIELD] previousSelectedAccessible
  [TYPE] interface javax.accessibility.Accessible
  [GENERICTYPE] interface javax.accessibility.Accessible
 [FIELD] editorAccessibleContext
  [TYPE] class javax.swing.JComboBox$AccessibleJComboBox$EditorAccessibleContext
Exception in thread "main" java.lang.reflect.GenericSignatureFormatError
        at sun.reflect.generics.parser.SignatureParser.error(SignatureParser.java:121)
        at sun.reflect.generics.parser.SignatureParser.parseSimpleClassTypeSignature(SignatureParser.java:280)
        at sun.reflect.generics.parser.SignatureParser.parseClassTypeSignatureSuffix(SignatureParser.java:288)
        at sun.reflect.generics.parser.SignatureParser.parseClassTypeSignature(SignatureParser.java:262)
        at sun.reflect.generics.parser.SignatureParser.parseFieldTypeSignature(SignatureParser.java:246)
        at sun.reflect.generics.parser.SignatureParser.parseTypeSignature(SignatureParser.java:377)
        at sun.reflect.generics.parser.SignatureParser.parseTypeSig(SignatureParser.java:175)
        at sun.reflect.generics.repository.FieldRepository.parse(FieldRepository.java:52)
        at sun.reflect.generics.repository.FieldRepository.parse(FieldRepository.java:42)
        at sun.reflect.generics.repository.AbstractRepository.<init>(AbstractRepository.java:74)
        at sun.reflect.generics.repository.FieldRepository.<init>(FieldRepository.java:48)
        at sun.reflect.generics.repository.FieldRepository.make(FieldRepository.java:66)
        at java.lang.reflect.Field.getGenericInfo(Field.java:98)
        at java.lang.reflect.Field.getGenericType(Field.java:236)
        at testapp.reflect.GenericSignatureFormatError.main(GenericSignatureFormatError.java:21)
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in JDK7b140, for instance, the code prints:
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Class = class javax.swing.JComboBox$AccessibleJComboBox
 [FIELD] popupList
  [TYPE] class javax.swing.JList
  [GENERICTYPE] class javax.swing.JList
 [FIELD] previousSelectedAccessible
  [TYPE] interface javax.accessibility.Accessible
  [GENERICTYPE] interface javax.accessibility.Accessible
 [FIELD] editorAccessibleContext
  [TYPE] class javax.swing.JComboBox$AccessibleJComboBox$EditorAccessibleContext
  [GENERICTYPE] class javax.swing.JComboBox$AccessibleJComboBox$EditorAccessibleContext
 [FIELD] this$0
  [TYPE] class javax.swing.JComboBox
  [GENERICTYPE] class javax.swing.JComboBox
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