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Part of my research is detecting design patterns in Java sources.</div>

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Therefore it is necessary to parse Java sources</div>

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I used the grammar specified in <a href="https://docs.oracle.com/javase/specs/jls/se20/html/index.html" id="LPlnk584635">https://docs.oracle.com/javase/specs/jls/se20/html/index.html</a>.</div>

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First, I made the grammar useful for the bottom-up parser generator cup (<a href="http://www2.cs.tum.edu/projects/cup/" id="LPlnk249011">http://www2.cs.tum.edu/projects/cup/</a>)</div>

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This resulted in more than 100 shifts/reduce and reduce/reduce conflicts.</div>

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Reduce/reduce conflicts and suggest grammar mistakes.</div>

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Second, I made the grammar useful for the top-down parser generator Grammatica (https://grammatica.percederberg.net).</div>

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This resulted in many errors because the LL () grammar is not valid.</div>

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An example:</div>

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The production rule for ClassOrInterfaceType and ClassType is:</div>

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<span class="lhs ContentPasted3" style="font-family: monospace; font-size: 12px; font-style: italic; background-color: rgb(211, 211, 211);">ClassOrInterfaceType:</span>

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<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-ClassType" title="ClassType" class="ContentPasted3" data-loopstyle="link">ClassType</a><br class="ContentPasted3">

<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-InterfaceType" title="InterfaceType" class="ContentPasted3">InterfaceType</a></div>

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<span class="lhs ContentPasted2" style="font-family: monospace; font-size: 12px; font-style: italic; background-color: rgb(211, 211, 211);">ClassType:</span>

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{<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-9.html#jls-Annotation" title="Annotation" class="ContentPasted2" data-loopstyle="link">Annotation</a>}<span class="ContentPasted2"> </span><a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-3.html#jls-TypeIdentifier" title="TypeIdentifier" class="ContentPasted2">TypeIdentifier</a><span class="ContentPasted2"> </span>[<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-TypeArguments" title="TypeArguments" class="ContentPasted2">TypeArguments</a>]<br class="ContentPasted2">

<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-6.html#jls-PackageName" title="PackageName" class="ContentPasted2">PackageName</a><span class="ContentPasted2"> </span><code class="literal ContentPasted2" style="font-style:normal">.</code><span class="ContentPasted2"> </span>{<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-9.html#jls-Annotation" title="Annotation" class="ContentPasted2">Annotation</a>}<span class="ContentPasted2"> </span><a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-3.html#jls-TypeIdentifier" title="TypeIdentifier" class="ContentPasted2">TypeIdentifier</a><span class="ContentPasted2"> </span>[<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-TypeArguments" title="TypeArguments" class="ContentPasted2">TypeArguments</a>]<br class="ContentPasted2">

<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-ClassOrInterfaceType" title="ClassOrInterfaceType" class="ContentPasted2">ClassOrInterfaceType</a><span class="ContentPasted2"> </span><code class="literal ContentPasted2" style="font-style:normal">.</code><span class="ContentPasted2"> </span>{<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-9.html#jls-Annotation" title="Annotation" class="ContentPasted2">Annotation</a>}<span class="ContentPasted2"> </span><a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-3.html#jls-TypeIdentifier" title="TypeIdentifier" class="ContentPasted2">TypeIdentifier</a><span class="ContentPasted2"> </span>[<a href="https://docs.oracle.com/javase/specs/jls/se20/html/jls-4.html#jls-TypeArguments" title="TypeArguments" class="ContentPasted2">TypeArguments</a>]</div>

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This results in an infinite loop: ClassOrInterfaceType produces a ClassType and  ClassType produces </div>

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ClassOrInterfaceType .....</div>

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Some production rules have more than one alternative which starts with @</div>

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which is not valid LL and can not be solved by looking ahead with more tokens.</div>

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Is a valid bottom-up grammar e.g. LALR(1) of top-down grammar LL(k) available?<br>

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ANTLR provides a LL() grammar for Java 9, that is of course out of date.</div>

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With regards,</div>

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Ed van Doorn</div>

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