http://www.javassist.org/: Javassist (JAVA programming ASSISTant) makes Java bytecode manipulation simple. It is a class library for editing bytecodes in Java. (Shigeru Chiba, www.javassist.org) 
/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later,
 * or the Apache License Version 2.0.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist;

import java.util.HashMap;

import javassist.bytecode.Descriptor;


A hash table associating class names with different names.

This hashtable is used for replacing class names in a class
definition or a method body.  Define a subclass of this class
if a more complex mapping algorithm is needed.  For example,

class MyClassMap extends ClassMap {
  public Object get(Object jvmClassName) {
    String name = toJavaName((String)jvmClassName);
    if (name.startsWith("java."))
        return toJvmName("java2." + name.substring(5));
    else
        return super.get(jvmClassName);
  }
}


This subclass maps java.lang.String to
java2.lang.String.  Note that get()
receives and returns the internal representation of a class name.
For example, the internal representation of java.lang.String
is java/lang/String.

Note that this is a map from String to String.

See Also:
/**
 * A hash table associating class names with different names.
 *
 * <p>This hashtable is used for replacing class names in a class
 * definition or a method body.  Define a subclass of this class
 * if a more complex mapping algorithm is needed.  For example,
 *
 * <pre>class MyClassMap extends ClassMap {
 *   public Object get(Object jvmClassName) {
 *     String name = toJavaName((String)jvmClassName);
 *     if (name.startsWith("java."))
 *         return toJvmName("java2." + name.substring(5));
 *     else
 *         return super.get(jvmClassName);
 *   }
 * }</pre>
 *
 * <p>This subclass maps <code>java.lang.String</code> to
 * <code>java2.lang.String</code>.  Note that <code>get()</code>
 * receives and returns the internal representation of a class name.
 * For example, the internal representation of <code>java.lang.String</code>
 * is <code>java/lang/String</code>.
 *
 * <p>Note that this is a map from <code>String</code> to <code>String</code>.
 *
 * @see #get(Object)
 * @see CtClass#replaceClassName(ClassMap)
 * @see CtNewMethod#copy(CtMethod,String,CtClass,ClassMap)
 */
public class ClassMap extends HashMap<String,String> {
    
default serialVersionUID 
/** default serialVersionUID */
    private static final long serialVersionUID = 1L;
    private ClassMap parent;

    
Constructs a hash table.

/**
     * Constructs a hash table.
     */
    public ClassMap() { parent = null; }

    ClassMap(ClassMap map) { parent = map; }

    
Maps a class name to another name in this hashtable.
The names are obtained with calling Class.getName().
This method translates the given class names into the
internal form used in the JVM before putting it in
the hashtable.

Params:
  • oldname –   the original class name
  • newname –   the substituted class name.
/**
     * Maps a class name to another name in this hashtable.
     * The names are obtained with calling <code>Class.getName()</code>.
     * This method translates the given class names into the
     * internal form used in the JVM before putting it in
     * the hashtable.
     *
     * @param oldname   the original class name
     * @param newname   the substituted class name.
     */
    public void put(CtClass oldname, CtClass newname) {
        put(oldname.getName(), newname.getName());
    }

    
Maps a class name to another name in this hashtable.
If the hashtable contains another mapping from the same
class name, the old mapping is replaced.
This method translates the given class names into the
internal form used in the JVM before putting it in
the hashtable.

If oldname is identical to
newname, then this method does not
perform anything; it does not record the mapping from
oldname to newname.  See
fix method.

Params:
  • oldname –   the original class name.
  • newname –   the substituted class name.
See Also:
/**
     * Maps a class name to another name in this hashtable.
     * If the hashtable contains another mapping from the same
     * class name, the old mapping is replaced.
     * This method translates the given class names into the
     * internal form used in the JVM before putting it in
     * the hashtable.
     *
     * <p>If <code>oldname</code> is identical to
     * <code>newname</code>, then this method does not
     * perform anything; it does not record the mapping from
     * <code>oldname</code> to <code>newname</code>.  See
     * <code>fix</code> method.
     *
     * @param oldname   the original class name.
     * @param newname   the substituted class name.
     * @see #fix(String)
     */
    @Override
    public String put(String oldname, String newname) {
        if (oldname == newname)
            return oldname;

        String oldname2 = toJvmName(oldname);
        String s = get(oldname2);
        if (s == null || !s.equals(oldname2))
            return super.put(oldname2, toJvmName(newname));
        return s;
    }

    
Is equivalent to put() except that
the given mapping is not recorded into the hashtable
if another mapping from oldname is
already included.

Params:
  • oldname –       the original class name.
  • newname –       the substituted class name.
/**
     * Is equivalent to <code>put()</code> except that
     * the given mapping is not recorded into the hashtable
     * if another mapping from <code>oldname</code> is
     * already included.
     *
     * @param oldname       the original class name.
     * @param newname       the substituted class name.
     */
    public void putIfNone(String oldname, String newname) {
        if (oldname == newname)
            return;

        String oldname2 = toJvmName(oldname);
        String s = get(oldname2);
        if (s == null)
            super.put(oldname2, toJvmName(newname));
    }

    protected final String put0(String oldname, String newname) {
        return super.put(oldname, newname);
    }

    
Returns the class name to wihch the given jvmClassName
is mapped.  A subclass of this class should override this method.

This method receives and returns the internal representation of
class name used in the JVM.

See Also:
/**
     * Returns the class name to wihch the given <code>jvmClassName</code>
     * is mapped.  A subclass of this class should override this method.
     *
     * <p>This method receives and returns the internal representation of
     * class name used in the JVM.
     *
     * @see #toJvmName(String)
     * @see #toJavaName(String)
     */
    @Override
    public String get(Object jvmClassName) {
        String found = super.get(jvmClassName);
        if (found == null && parent != null)
            return parent.get(jvmClassName);
        return found;
    }
    
Prevents a mapping from the specified class name to another name.

/**
     * Prevents a mapping from the specified class name to another name.
     */
    public void fix(CtClass clazz) {
        fix(clazz.getName());
    }

    
Prevents a mapping from the specified class name to another name.

/**
     * Prevents a mapping from the specified class name to another name.
     */
    public void fix(String name) {
        String name2 = toJvmName(name);
        super.put(name2, name2);
    }

    
Converts a class name into the internal representation used in
the JVM.

/**
     * Converts a class name into the internal representation used in
     * the JVM.
     */
    public static String toJvmName(String classname) {
        return Descriptor.toJvmName(classname);
    }

    
Converts a class name from the internal representation used in
the JVM to the normal one used in Java.

/**
     * Converts a class name from the internal representation used in
     * the JVM to the normal one used in Java.
     */
    public static String toJavaName(String classname) {
        return Descriptor.toJavaName(classname);
    }
}