code: public @CheckForNull
      XClass getXClass(ClassDescriptor classDescriptor) {
          try {
              IAnalysisCache analysisCache = Global.getAnalysisCache();
              return analysisCache.getClassAnalysis(XClass.class, classDescriptor);
          } catch (CheckedAnalysisException e) {
              return null;
          }
      }
docs: Get the XClass object providing information about the class named by the
  given ClassDescriptor.
  
  @param classDescriptor
  a ClassDescriptor
  @return an XClass object providing information about the class, or null
  if the class cannot be found