#vulnerable code 
                               @Override
   public boolean isReturnTypeVoid()
   {
      return getReturnType().isType(Void.TYPE);
   } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                               @Override
   public boolean isReturnTypeVoid()
   {
      return getReturnType() == null || getReturnType().isType(Void.TYPE);
   }