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Java example source code file (SystemDictionaryHelper.java)

This example Java source code file (SystemDictionaryHelper.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

comparator, instanceklass, object, observer, string, symbol, systemdictionary, systemdictionaryhelper, util, vector

The SystemDictionaryHelper.java Java example source code

/*
 * Copyright (c) 2002, 2005, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

package sun.jvm.hotspot.utilities;

import java.util.*;
import sun.jvm.hotspot.oops.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.runtime.*;

public class SystemDictionaryHelper {
   static {
      VM.registerVMInitializedObserver(new Observer() {
         public void update(Observable o, Object data) {
            initialize();
         }
      });
   }

   private static synchronized void initialize() {
      klasses = null;
   }

   // Instance klass array sorted by name.
   private static InstanceKlass[] klasses;

   // side-effect!. caches the instance klass array.
   public static synchronized InstanceKlass[] getAllInstanceKlasses() {
      if (klasses != null) {
         return klasses;
      }

      final Vector tmp = new Vector();
      SystemDictionary dict = VM.getVM().getSystemDictionary();
      dict.classesDo(new SystemDictionary.ClassVisitor() {
                        public void visit(Klass k) {
                           if (k instanceof InstanceKlass) {
                              InstanceKlass ik = (InstanceKlass) k;
                              tmp.add(ik);
                           }
                        }
                     });

      Object[] tmpArray = tmp.toArray();
      klasses = new InstanceKlass[tmpArray.length];
      System.arraycopy(tmpArray, 0, klasses, 0, tmpArray.length);
      Arrays.sort(klasses, new Comparator() {
                          public int compare(Object o1, Object o2) {
                             InstanceKlass k1 = (InstanceKlass) o1;
                             InstanceKlass k2 = (InstanceKlass) o2;
                             Symbol s1 = k1.getName();
                             Symbol s2 = k2.getName();
                             return s1.asString().compareTo(s2.asString());
                          }
                      });
      return klasses;
   }

   // returns array of instance klasses whose name contains given namePart
   public static InstanceKlass[] findInstanceKlasses(String namePart) {
      namePart = namePart.replace('.', '/');
      InstanceKlass[] tmpKlasses = getAllInstanceKlasses();

      Vector tmp = new Vector();
      for (int i = 0; i < tmpKlasses.length; i++) {
         String name = tmpKlasses[i].getName().asString();
         if (name.indexOf(namePart) != -1) {
            tmp.add(tmpKlasses[i]);
         }
      }

      Object[] tmpArray = tmp.toArray();
      InstanceKlass[] searchResult = new InstanceKlass[tmpArray.length];
      System.arraycopy(tmpArray, 0, searchResult, 0, tmpArray.length);
      return searchResult;
   }

   // find first class whose name matches exactly the given argument.
   public static InstanceKlass findInstanceKlass(String className) {
      // convert to internal name
      className = className.replace('.', '/');
      SystemDictionary sysDict = VM.getVM().getSystemDictionary();

      // check whether we have a bootstrap class of given name
      Klass klass = sysDict.find(className, null, null);
      if (klass != null) {
         return (InstanceKlass) klass;
      }

      // check whether we have a system class of given name
      klass = sysDict.find(className, sysDict.javaSystemLoader(), null);
      if (klass != null) {
         return (InstanceKlass) klass;
      }

      // didn't find bootstrap or system class of given name.
      // search through the entire dictionary..
      InstanceKlass[] tmpKlasses = getAllInstanceKlasses();
      // instance klass array is sorted by name. do binary search
      int low = 0;
      int high = tmpKlasses.length-1;

      int mid = -1;
      while (low <= high) {
         mid = (low + high) >> 1;
         InstanceKlass midVal = tmpKlasses[mid];
         int cmp = midVal.getName().asString().compareTo(className);

         if (cmp < 0) {
             low = mid + 1;
         } else if (cmp > 0) {
             high = mid - 1;
         } else { // match found
             return tmpKlasses[mid];
         }
      }
      // no match ..
      return null;
   }
}

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