title: JavaDoc generation in Android Studio: NullPointerException
body: <p>When trying to generate JavaDoc in Android Studio, it acts up and shows countless errors concerning non-existing packages and unknown symbols (mostly Android-related stuff).</p>
  
  <p>Finally I get this error message:</p>
  
  <pre><code>Standard Doclet version 1.7.0_55
  Building tree for all the packages and classes...
  java.lang.NullPointerException
      at com.sun.tools.javadoc.TypeMaker.getType(TypeMaker.java:83)
      at com.sun.tools.javadoc.TypeMaker.getType(TypeMaker.java:44)
      at com.sun.tools.javadoc.ClassDocImpl.superclassType(ClassDocImpl.java:496)
      at com.sun.tools.doclets.internal.toolkit.util.Util.getAllInterfaces(Util.java:459)
      at com.sun.tools.doclets.internal.toolkit.util.Util.getAllInterfaces(Util.java:497)
      at com.sun.tools.doclets.internal.toolkit.util.ClassTree.processType(ClassTree.java:194)
      at com.sun.tools.doclets.internal.toolkit.util.ClassTree.buildTree(ClassTree.java:146)
      at com.sun.tools.doclets.internal.toolkit.util.ClassTree.&lt;init&gt;(ClassTree.java:91)
      at com.sun.tools.doclets.internal.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:123)
      at com.sun.tools.doclets.internal.toolkit.AbstractDoclet.start(AbstractDoclet.java:83)
      at com.sun.tools.doclets.formats.html.HtmlDoclet.start(HtmlDoclet.java:63)
      at com.sun.tools.doclets.standard.Standard.start(Standard.java:39)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:606)
      at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:280)
      at com.sun.tools.javadoc.DocletInvoker.start(DocletInvoker.java:160)
      at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:397)
      at com.sun.tools.javadoc.Start.begin(Start.java:167)
      at com.sun.tools.javadoc.Main.execute(Main.java:59)
      at com.sun.tools.javadoc.Main.main(Main.java:49)
  342 warnings
  
  javadoc exited with exit code 1
  </code></pre>