001/* GarbageCollectorMXBean.java - Interface for a garbage collector bean
002   Copyright (C) 2006 Free Software Foundation
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.lang.management;
039
040/**
041 * Provides access to information about the garbage collectors
042 * of the virtual machine.  Garbage collectors are responsible
043 * for removing unreferenced objects from memory.  A garbage
044 * collector is a type of memory manager, so this interface
045 * is combined with that of generic memory managers.  An instance
046 * of this bean for each garbage collector is obtained by calling
047 * {@link ManagementFactory#getGarbageCollectorMXBeans()}.
048 *
049 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
050 * @since 1.5
051 */
052public interface GarbageCollectorMXBean
053  extends MemoryManagerMXBean
054{
055
056  /**
057   * Returns the number of collections the garbage collector
058   * represented by this bean has made.  -1 is returned if the
059   * collection count is undefined.
060   *
061   * @return the number of collections made, or -1 if this is
062   *         undefined.
063   */
064  long getCollectionCount();
065
066  /**
067   * Returns the accumulated number of milliseconds this garbage
068   * collector has spent freeing the memory used by unreferenced
069   * objects.  -1 is returned if the collection time is undefined.
070   * Note that the accumulated time may not change, even when the
071   * collection count increases, if the time taken is sufficiently
072   * short; this depends on the resolution of the timer used.
073   * 
074   * @return the accumulated number of milliseconds spent collecting,
075   *         or -1 if this is undefined.
076   */
077  long getCollectionTime();
078
079}