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com.hfg xml, html, svg, and bioinformatics utility library
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package com.hfg.util;


import java.io.DataInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.StandardLocation;
import javax.tools.ToolProvider;

//------------------------------------------------------------------------------
/**
 General utility for exploring java classes.
 
 @author J. Alex Taylor, hairyfatguy.com
 
 */
//------------------------------------------------------------------------------
// com.hfg XML/HTML Coding Library
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// J. Alex Taylor, President, Founder, CEO, COO, CFO, OOPS hairyfatguy.com
// [email protected]
//------------------------------------------------------------------------------

public class ClassExplorer
{
   private Map> mIsAssignableFromMap;

   //###########################################################################
   // PUBLIC METHODS
   //###########################################################################

   //--------------------------------------------------------------------------
   public List findExtendingClasses(Class inBaseClass)
         throws IOException
   {
      List extendingClassnames = new ArrayList<>(20);
      recursiveFindExtendingClasses(inBaseClass.getName(), extendingClassnames);

      return extendingClassnames;
   }

   //###########################################################################
   // PRIVATE METHODS
   //###########################################################################

   //--------------------------------------------------------------------------
   private void recursiveFindExtendingClasses(String inBaseClass, List inExtendingClasses)
         throws IOException
   {
      Set extendingClasses = getIsAssignableFromMap().get(inBaseClass);
      if (extendingClasses != null)
      {
         inExtendingClasses.addAll(extendingClasses);
         for (String classname : extendingClasses)
         {
            recursiveFindExtendingClasses(classname, inExtendingClasses);
         }
      }
   }

   //--------------------------------------------------------------------------
   private synchronized Map> getIsAssignableFromMap()
         throws IOException
   {
      if (null == mIsAssignableFromMap)
      {
         mIsAssignableFromMap = buildCache();
      }

      return mIsAssignableFromMap;
   }

   //--------------------------------------------------------------------------
   private Map> buildCache()
         throws IOException
   {
      Map> assignableFromMap = new HashMap<>();

      final StandardJavaFileManager fileManager = ToolProvider.getSystemJavaCompiler().getStandardFileManager(null, null, null);
      for (JavaFileObject javaFileObj : fileManager.list(StandardLocation.CLASS_PATH, "", Collections.singleton(JavaFileObject.Kind.CLASS), true))
      {
         if (javaFileObj.getName().contains("ct.sym("))
         {
            // Don't process the linking lib
            continue;
         }

         DataInputStream stream = null;
         try
         {
            stream = new DataInputStream(javaFileObj.openInputStream());
            BasicClassFileInfo classInfo = new BasicClassFileInfo(stream);

            if (! classInfo.getSuperClassname().equals(Object.class.getName()))
            {
               Set extendingOrImplementingClasses = assignableFromMap.get(classInfo.getSuperClassname());
               if (null == extendingOrImplementingClasses)
               {
                  extendingOrImplementingClasses = new HashSet<>(10);
                  assignableFromMap.put(classInfo.getSuperClassname(), extendingOrImplementingClasses);
               }

               extendingOrImplementingClasses.add(classInfo.getClassname());
            }

            String[] interfaces = classInfo.getInterfaceClassnames();
            if (interfaces != null)
            {
               for (String interfaceName : interfaces)
               {
                  Set extendingOrImplementingClasses = assignableFromMap.get(interfaceName);
                  if (null == extendingOrImplementingClasses)
                  {
                     extendingOrImplementingClasses = new HashSet<>(5);
                     assignableFromMap.put(interfaceName, extendingOrImplementingClasses);
                  }

                  extendingOrImplementingClasses.add(classInfo.getClassname());
               }
            }
         }
         catch (Throwable e)
         {
//               System.out.println(fullClassName);
         }
         finally
         {
            if (stream != null)
            {
               stream.close();
            }
         }
      }

      return assignableFromMap;
   }
}