Since JDK7b130.
If the following annotation processor:

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@SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes("*")
public class Processor extends AbstractProcessor {

    private Set<? extends Element> rootElements;

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        Messager m = processingEnv.getMessager();
        if (roundEnv.processingOver()) {
            Set<? extends Element> elements = rootElements;
            for (Element element : elements) {
                m.printMessage(Kind.NOTE, "- Root element name: " + element.getSimpleName());

                for (Element e : ElementFilter.fieldsIn(element.getEnclosedElements())) {
                    m.printMessage(Kind.NOTE, "- Field name: " + e.getSimpleName());
(1) Object o = ((VariableElement)e).getConstantValue();
(2) m.printMessage(Kind.NOTE, "- Value: " + o);
                }
            }
        } else {
            rootElements = roundEnv.getRootElements();
        }
        return true;
    }
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is applied to the following source:

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public interface ValidInterface {
    int integerField = 1;
}
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Then the output is:

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java.lang.IllegalStateException
        at com.sun.tools.javac.util.Context.checkState(Context.java:205)
        at com.sun.tools.javac.util.Context.get(Context.java:141)
        at com.sun.tools.javac.code.Symtab.instance(Symtab.java:57)
        at com.sun.tools.javac.code.Lint$AugmentVisitor.initSyms(Lint.java:298)
        at com.sun.tools.javac.code.Lint$AugmentVisitor.augment(Lint.java:287)
        at com.sun.tools.javac.code.Lint.augment(Lint.java:82)
        at com.sun.tools.javac.comp.Attr.attribLazyConstantValue(Attr.java:597)
        at com.sun.tools.javac.code.Symbol$VarSymbol$1.call(Symbol.java:973)
        at com.sun.tools.javac.code.Symbol$VarSymbol.getConstValue(Symbol.java:1005)
        at com.sun.tools.javac.code.Symbol$VarSymbol.getConstantValue(Symbol.java:964)
        at test.Processor.process(Processor.java:44)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:786)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$200(JavacProcessingEnvironment.java:94)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$DiscoveredProcessors$ProcessorStateIterator.runContributingProcs(JavacProcessingEnvironment.java:637)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1010)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1157)
        at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1085)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:801)
        at com.sun.tools.javac.main.Main.compile(Main.java:411)
        at com.sun.tools.javac.main.Main.compile(Main.java:329)
        at com.sun.tools.javac.main.Main.compile(Main.java:320)
        at com.sun.tools.javac.Main.compile(Main.java:76)
        at com.sun.tools.javac.Main.main(Main.java:61)


An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.AssertionError: java.lang.IllegalStateException
        at com.sun.tools.javac.code.Symbol$VarSymbol.getConstValue(Symbol.java:1008)
        at com.sun.tools.javac.code.Symbol$VarSymbol.getConstantValue(Symbol.java:964)
        at test.Processor.process(Processor.java:44)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:786)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$200(JavacProcessingEnvironment.java:94)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$DiscoveredProcessors$ProcessorStateIterator.runContributingProcs(JavacProcessingEnvironment.java:637)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1010)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1157)
        at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1085)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:801)
        at com.sun.tools.javac.main.Main.compile(Main.java:411)
        at com.sun.tools.javac.main.Main.compile(Main.java:329)
        at com.sun.tools.javac.main.Main.compile(Main.java:320)
        at com.sun.tools.javac.Main.compile(Main.java:76)
        at com.sun.tools.javac.Main.main(Main.java:61)
Caused by: java.lang.IllegalStateException
        at com.sun.tools.javac.util.Context.checkState(Context.java:205)
        at com.sun.tools.javac.util.Context.get(Context.java:141)
        at com.sun.tools.javac.code.Symtab.instance(Symtab.java:57)
        at com.sun.tools.javac.code.Lint$AugmentVisitor.initSyms(Lint.java:298)
        at com.sun.tools.javac.code.Lint$AugmentVisitor.augment(Lint.java:287)
        at com.sun.tools.javac.code.Lint.augment(Lint.java:82)
        at com.sun.tools.javac.comp.Attr.attribLazyConstantValue(Attr.java:597)
        at com.sun.tools.javac.code.Symbol$VarSymbol$1.call(Symbol.java:973)
        at com.sun.tools.javac.code.Symbol$VarSymbol.getConstValue(Symbol.java:1005)
        ... 14 more

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If one comments lines (1),(2) then the output is:

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Note: - Root element name: ValidInterface
Note: - Field name: integerField
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