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 *  Copyright 2020 Adobe
 *  All Rights Reserved.
 *
 * NOTICE: All information contained herein is, and remains
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package com.day.util;

import java.util.Stack;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The FinalizerHandler class implements the functionality to
 * register {@link Finalizer}s and call them at some point in time, such as
 * the end of the current ExecutionContext.
 * 
 * The registered {@link Finalizer}s will be called in the reverse sequence
 * of their registration. That is the last {@link Finalizer} registered will
 * get called first.
 *
 * @version $Revision: 1.13 $, $Date: 2004-08-22 06:56:09 +0200 (Sun, 22 Aug 2004) $
 * @author fmeschbe
 * @since antbear
 * Audience dev
 */
public class FinalizerHandler {

    /** default log */
    private static final Logger log =
        LoggerFactory.getLogger(FinalizerHandler.class);

    /** Keep the list of registered objects in this Stack. */
    private final Stack registered = new Stack();

    /**
     * Registers a Finalizer.
     * @param object the finalzier to register
     */
    public void registerObject(Finalizer object) {
        registered.push(object);
    }

    /**
     * Unregisters a Finalizer object. After unregistering the
     * objects doFinalize() method is not called anymore.
     *
     * @param object The Finalizer object to unregister.
     */
    public void unregister(Finalizer object) {
        registered.remove(object);
    }

    /**
     * Unregisters all registered Finalizer objects so that a
     * subsequent call to {@link #callFinalizers()} effectively does nothing.
     */
    public void unregisterAll() {
        registered.clear();
    }

    /**
     * Returns true if no {@link Finalizer} objects are registered
     * yet.
     * @return whether it's empty
     */
    public boolean isEmpty() {
        return registered.isEmpty();
    }

    /**
     * Calls all registered Finalizer {@link Finalizer#doFinalize()}
     * method, and removes them from the internal list.
     * 
     * The call to the {@link Finalizer#doFinalize()} is not expected to throw
     * any exceptions or even errors. In case a Throwable is thrown
     * this is logged as an error and processing continiues with the next
     * Finalizer to be finalized.
     */
    public void callFinalizers() {

        while (!registered.isEmpty()) {

            Finalizer fin = (Finalizer) registered.pop();

            try {

                fin.doFinalize();

            } catch (Throwable t) {

                // ignore anything thrown
                log.error("callFinalizers: Unexpected Exception/Error: {}",
                    t.toString());
                log.debug("dump", t);

            }
        }
    }
}