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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
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25  
26  package java.lang.management;
27  
28  /**
29   * The management interface for the garbage collection of
30   * the Java virtual machine.  Garbage collection is the process
31   * that the Java virtual machine uses to find and reclaim unreachable
32   * objects to free up memory space.  A garbage collector is one type of
33   * {@link MemoryManagerMXBean memory manager}.
34   *
35   * <p> A Java virtual machine may have one or more instances of
36   * the implementation class of this interface.
37   * An instance implementing this interface is
38   * an <a href="ManagementFactory.html#MXBean">MXBean</a>
39   * that can be obtained by calling
40   * the {@link ManagementFactory#getGarbageCollectorMXBeans} method or
41   * from the {@link ManagementFactory#getPlatformMBeanServer
42   * platform <tt>MBeanServer</tt>} method.
43   *
44   * <p>The <tt>ObjectName</tt> for uniquely identifying the MXBean for
45   * a garbage collector within an MBeanServer is:
46   * <blockquote>
47   *   {@link ManagementFactory#GARBAGE_COLLECTOR_MXBEAN_DOMAIN_TYPE
48   *    <tt>java.lang:type=GarbageCollector</tt>}<tt>,name=</tt><i>collector's name</i>
49   * </blockquote>
50   *
51   * It can be obtained by calling the
52   * {@link PlatformManagedObject#getObjectName} method.
53   *
54   * A platform usually includes additional platform-dependent information
55   * specific to a garbage collection algorithm for monitoring.
56   *
57   * @see ManagementFactory#getPlatformMXBeans(Class)
58   * @see MemoryMXBean
59   *
60   * @see <a href="../../../javax/management/package-summary.html">
61   *      JMX Specification.</a>
62   * @see <a href="package-summary.html#examples">
63   *      Ways to Access MXBeans</a>
64   *
65   * @author  Mandy Chung
66   * @since   1.5
67   */
68  public interface GarbageCollectorMXBean extends MemoryManagerMXBean {
69      /**
70       * Returns the total number of collections that have occurred.
71       * This method returns <tt>-1</tt> if the collection count is undefined for
72       * this collector.
73       *
74       * @return the total number of collections that have occurred.
75       */
76      public long getCollectionCount();
77  
78      /**
79       * Returns the approximate accumulated collection elapsed time
80       * in milliseconds.  This method returns <tt>-1</tt> if the collection
81       * elapsed time is undefined for this collector.
82       * <p>
83       * The Java virtual machine implementation may use a high resolution
84       * timer to measure the elapsed time.  This method may return the
85       * same value even if the collection count has been incremented
86       * if the collection elapsed time is very short.
87       *
88       * @return the approximate accumulated collection elapsed time
89       * in milliseconds.
90       */
91      public long getCollectionTime();
92  
93  
94  }