protected  void initialize(Class type,
    Object oldInstance,
    Object newInstance,
    Encoder out) 
{
        // System.out.println("Initializing: " + newInstance);
        java.util.Map oldMap = (java.util.Map)oldInstance;
        java.util.Map newMap = (java.util.Map)newInstance;
        // Remove the new elements.
        // Do this first otherwise we undo the adding work.
        if (newMap != null) {
            for ( Object newKey : newMap.keySet() ) {
               // PENDING: This "key" is not in the right environment.
                if (!oldMap.containsKey(newKey)) {
                    invokeStatement(oldInstance, "remove", new Object[]{newKey}, out);
                }
            }
        }
        // Add the new elements.
        for ( Object oldKey : oldMap.keySet() ) {
            Expression oldGetExp = new Expression(oldInstance, "get", new Object[]{oldKey});
            // Pending: should use newKey.
            Expression newGetExp = new Expression(newInstance, "get", new Object[]{oldKey});
            try {
                Object oldValue = oldGetExp.getValue();
                Object newValue = newGetExp.getValue();
                out.writeExpression(oldGetExp);
                if (!MetaData.equals(newValue, out.get(oldValue))) {
                    invokeStatement(oldInstance, "put", new Object[]{oldKey, oldValue}, out);
                } else if ((newValue == null) && !newMap.containsKey(oldKey)) {
                    // put oldValue(=null?) if oldKey is absent in newMap
                    invokeStatement(oldInstance, "put", new Object[]{oldKey, oldValue}, out);
                }
            }
            catch (Exception e) {
                out.getExceptionListener().exceptionThrown(e);
            }
        }
}