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	/*
	* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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	package java.lang.management;

	/**
	* The management interface for a memory pool. A memory pool
	* represents the memory resource managed by the Java virtual machine
	* and is managed by one or more {@link MemoryManagerMXBean memory managers}.
	*
	* <p> A Java virtual machine has one or more instances of the
	* implementation class of this interface. An instance
	* implementing this interface is
	* an <a href="ManagementFactory.html#MXBean">MXBean</a>
	* that can be obtained by calling
	* the {@link ManagementFactory#getMemoryPoolMXBeans} method or
	* from the {@link ManagementFactory#getPlatformMBeanServer
	* platform <tt>MBeanServer</tt>} method.
	*
	* <p>The <tt>ObjectName</tt> for uniquely identifying the MXBean for
	* a memory pool within an <tt>MBeanServer</tt> is:
	* <blockquote>
	* {@link ManagementFactory#MEMORY_POOL_MXBEAN_DOMAIN_TYPE
	* <tt>java.lang:type=MemoryPool</tt>}<tt>,name=</tt><i>pool's name</i>
	* </blockquote>
	*
	* It can be obtained by calling the
	* {@link PlatformManagedObject#getObjectName} method.
	*
	* <h3>Memory Type</h3>
	* <p>The Java virtual machine has a heap for object allocation and also
	* maintains non-heap memory for the method area and the Java virtual
	* machine execution. The Java virtual machine can have one or more
	* memory pools. Each memory pool represents a memory area
	* of one of the following types:
	* <ul>
	* <li>{@link MemoryType#HEAP heap}</li>
	* <li>{@link MemoryType#NON_HEAP non-heap}</li>
	* </ul>
	*
	* <h3>Memory Usage Monitoring</h3>
	*
	* A memory pool has the following attributes:
	* <ul>
	* <li><a href="#Usage">Memory usage</a></li>
	* <li><a href="#PeakUsage">Peak memory usage</a></li>
	* <li><a href="#UsageThreshold">Usage Threshold</a></li>
	* <li><a href="#CollectionThreshold">Collection Usage Threshold</a>
	* (only supported by some <em>garbage-collected</em> memory pools)</li>
	* </ul>
	*
	* <h3><a name="Usage">1. Memory Usage</a></h3>
	*
	* The {@link #getUsage} method provides an estimate
	* of the current usage of a memory pool.
	* For a garbage-collected memory pool, the amount of used memory
	* includes the memory occupied by all objects in the pool
	* including both <em>reachable</em> and <em>unreachable</em> objects.
	*
	* <p>In general, this method is a lightweight operation for getting
	* an approximate memory usage. For some memory pools, for example,
	* when objects are not packed contiguously, this method may be
	* an expensive operation that requires some computation to determine
	* the current memory usage. An implementation should document when
	* this is the case.
	*
	* <h3><a name="PeakUsage">2. Peak Memory Usage</a></h3>
	*
	* The Java virtual machine maintains the peak memory usage of a memory
	* pool since the virtual machine was started or the peak was reset.
	* The peak memory usage is returned by the {@link #getPeakUsage} method
	* and reset by calling the {@link #resetPeakUsage} method.
	*
	* <h3><a name="UsageThreshold">3. Usage Threshold</a></h3>
	*
	* Each memory pool has a manageable attribute
	* called the <i>usage threshold</i> which has a default value supplied
	* by the Java virtual machine. The default value is platform-dependent.
	* The usage threshold can be set via the
	* {@link #setUsageThreshold setUsageThreshold} method.
	* If the threshold is set to a positive value, the usage threshold crossing
	* checking is enabled in this memory pool.
	* If the usage threshold is set to zero, usage
	* threshold crossing checking on this memory pool is disabled.
	* The {@link MemoryPoolMXBean#isUsageThresholdSupported} method can
	* be used to determine if this functionality is supported.
	* <p>
	* A Java virtual machine performs usage threshold crossing checking on a
	* memory pool basis at its best appropriate time, typically,
	* at garbage collection time.
	* Each memory pool maintains a {@link #getUsageThresholdCount
	* usage threshold count} that will get incremented
	* every time when the Java virtual machine
	* detects that the memory pool usage is crossing the threshold.
	* <p>
	* This manageable usage threshold attribute is designed for monitoring the
	* increasing trend of memory usage with low overhead.
	* Usage threshold may not be appropriate for some memory pools.
	* For example, a generational garbage collector, a common garbage collection
	* algorithm used in many Java virtual machine implementations,
	* manages two or more generations segregating objects by age.
	* Most of the objects are allocated in
	* the <em>youngest generation</em> (say a nursery memory pool).
	* The nursery memory pool is designed to be filled up and
	* collecting the nursery memory pool will free most of its memory space
	* since it is expected to contain mostly short-lived objects
	* and mostly are unreachable at garbage collection time.
	* In this case, it is more appropriate for the nursery memory pool
	* not to support a usage threshold. In addition,
	* if the cost of an object allocation
	* in one memory pool is very low (for example, just atomic pointer exchange),
	* the Java virtual machine would probably not support the usage threshold
	* for that memory pool since the overhead in comparing the usage with
	* the threshold is higher than the cost of object allocation.
	*
	* <p>
	* The memory usage of the system can be monitored using
	* <a href="#Polling">polling</a> or
	* <a href="#ThresholdNotification">threshold notification</a> mechanisms.
	*
	* <ol type="a">
	* <li><a name="Polling"><b>Polling</b></a>
	* <p>
	* An application can continuously monitor its memory usage
	* by calling either the {@link #getUsage} method for all
	* memory pools or the {@link #isUsageThresholdExceeded} method
	* for those memory pools that support a usage threshold.
	* Below is example code that has a thread dedicated for
	* task distribution and processing. At every interval,
	* it will determine if it should receive and process new tasks based
	* on its memory usage. If the memory usage exceeds its usage threshold,
	* it will redistribute all outstanding tasks to other VMs and
	* stop receiving new tasks until the memory usage returns
	* below its usage threshold.
	*
	* <pre>
	* // Assume the usage threshold is supported for this pool.
	* // Set the threshold to myThreshold above which no new tasks
	* // should be taken.
	* pool.setUsageThreshold(myThreshold);
	* ....
	*
	* boolean lowMemory = false;
	* while (true) {
	* if (pool.isUsageThresholdExceeded()) {
	* // potential low memory, so redistribute tasks to other VMs
	* lowMemory = true;
	* redistributeTasks();
	* // stop receiving new tasks
	* stopReceivingTasks();
	* } else {
	* if (lowMemory) {
	* // resume receiving tasks
	* lowMemory = false;
	* resumeReceivingTasks();
	* }
	* // processing outstanding task
	* ...
	* }
	* // sleep for sometime
	* try {
	* Thread.sleep(sometime);
	* } catch (InterruptedException e) {
	* ...
	* }
	* }
	* </pre>
	*
	* <hr>
	* The above example does not differentiate the case where
	* the memory usage has temporarily dropped below the usage threshold
	* from the case where the memory usage remains above the threshold
	* between two iterations. The usage threshold count returned by
	* the {@link #getUsageThresholdCount} method
	* can be used to determine
	* if the memory usage has returned below the threshold
	* between two polls.
	* <p>
	* Below shows another example that takes some action if a
	* memory pool is under low memory and ignores the memory usage
	* changes during the action processing time.
	*
	* <pre>
	* // Assume the usage threshold is supported for this pool.
	* // Set the threshold to myThreshold which determines if
	* // the application will take some action under low memory condition.
	* pool.setUsageThreshold(myThreshold);
	*
	* int prevCrossingCount = 0;
	* while (true) {
	* // A busy loop to detect when the memory usage
	* // has exceeded the threshold.
	* while (!pool.isUsageThresholdExceeded() \|\|
	* pool.getUsageThresholdCount() == prevCrossingCount) {
	* try {
	* Thread.sleep(sometime)
	* } catch (InterruptException e) {
	* ....
	* }
	* }
	*
	* // Do some processing such as check for memory usage
	* // and issue a warning
	* ....
	*
	* // Gets the current threshold count. The busy loop will then
	* // ignore any crossing of threshold happens during the processing.
	* prevCrossingCount = pool.getUsageThresholdCount();
	* }
	* </pre><hr>
	* </li>
	* <li><a name="ThresholdNotification"><b>Usage Threshold Notifications</b></a>
	* <p>
	* Usage threshold notification will be emitted by {@link MemoryMXBean}.
	* When the Java virtual machine detects that the memory usage of
	* a memory pool has reached or exceeded the usage threshold
	* the virtual machine will trigger the <tt>MemoryMXBean</tt> to emit an
	* {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED
	* usage threshold exceeded notification}.
	* Another usage threshold exceeded notification will not be
	* generated until the usage has fallen below the threshold and
	* then exceeded it again.
	* <p>
	* Below is an example code implementing the same logic as the
	* first example above but using the usage threshold notification
	* mechanism to detect low memory conditions instead of polling.
	* In this example code, upon receiving notification, the notification
	* listener notifies another thread to perform the actual action
	* such as to redistribute outstanding tasks, stop receiving tasks,
	* or resume receiving tasks.
	* The <tt>handleNotification</tt> method should be designed to
	* do a very minimal amount of work and return without delay to avoid
	* causing delay in delivering subsequent notifications. Time-consuming
	* actions should be performed by a separate thread.
	* The notification listener may be invoked by multiple threads
	* concurrently; so the tasks performed by the listener
	* should be properly synchronized.
	*
	* <pre>
	* class MyListener implements javax.management.NotificationListener {
	* public void handleNotification(Notification notification, Object handback) {
	* String notifType = notification.getType();
	* if (notifType.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
	* // potential low memory, notify another thread
	* // to redistribute outstanding tasks to other VMs
	* // and stop receiving new tasks.
	* lowMemory = true;
	* notifyAnotherThread(lowMemory);
	* }
	* }
	* }
	*
	* // Register MyListener with MemoryMXBean
	* MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
	* NotificationEmitter emitter = (NotificationEmitter) mbean;
	* MyListener listener = new MyListener();
	* emitter.addNotificationListener(listener, null, null);
	*
	* // Assume this pool supports a usage threshold.
	* // Set the threshold to myThreshold above which no new tasks
	* // should be taken.
	* pool.setUsageThreshold(myThreshold);
	*
	* // Usage threshold detection is enabled and notification will be
	* // handled by MyListener. Continue for other processing.
	* ....
	*
	* </pre>
	* <hr>
	* <p>
	* There is no guarantee about when the <tt>MemoryMXBean</tt> will emit
	* a threshold notification and when the notification will be delivered.
	* When a notification listener is invoked, the memory usage of
	* the memory pool may have crossed the usage threshold more
	* than once.
	* The {@link MemoryNotificationInfo#getCount} method returns the number
	* of times that the memory usage has crossed the usage threshold
	* at the point in time when the notification was constructed.
	* It can be compared with the current usage threshold count returned
	* by the {@link #getUsageThresholdCount} method to determine if
	* such situation has occurred.
	* </li>
	* </ol>
	*
	* <h3><a name="CollectionThreshold">4. Collection Usage Threshold</a></h3>
	*
	* Collection usage threshold is a manageable attribute only applicable
	* to some garbage-collected memory pools.
	* After a Java virtual machine has expended effort in reclaiming memory
	* space by recycling unused objects in a memory pool at garbage collection
	* time, some number of bytes in the memory pools that are garbaged
	* collected will still be in use. The collection usage threshold
	* allows a value to be set for this number of bytes such
	* that if the threshold is exceeded,
	* a {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED
	* collection usage threshold exceeded notification}
	* will be emitted by the {@link MemoryMXBean}.
	* In addition, the {@link #getCollectionUsageThresholdCount
	* collection usage threshold count} will then be incremented.
	*
	* <p>
	* The {@link MemoryPoolMXBean#isCollectionUsageThresholdSupported} method can
	* be used to determine if this functionality is supported.
	*
	* <p>
	* A Java virtual machine performs collection usage threshold checking
	* on a memory pool basis. This checking is enabled if the collection
	* usage threshold is set to a positive value.
	* If the collection usage threshold is set to zero, this checking
	* is disabled on this memory pool. Default value is zero.
	* The Java virtual machine performs the collection usage threshold
	* checking at garbage collection time.
	*
	* <p>
	* Some garbage-collected memory pools may
	* choose not to support the collection usage threshold. For example,
	* a memory pool is only managed by a continuous concurrent garbage
	* collector. Objects can be allocated in this memory pool by some thread
	* while the unused objects are reclaimed by the concurrent garbage
	* collector simultaneously. Unless there is a well-defined
	* garbage collection time which is the best appropriate time
	* to check the memory usage, the collection usage threshold should not
	* be supported.
	*
	* <p>
	* The collection usage threshold is designed for monitoring the memory usage
	* after the Java virtual machine has expended effort in reclaiming
	* memory space. The collection usage could also be monitored
	* by the polling and threshold notification mechanism
	* described above for the <a href="#UsageThreshold">usage threshold</a>
	* in a similar fashion.
	*
	* @see ManagementFactory#getPlatformMXBeans(Class)
	* @see <a href="../../../javax/management/package-summary.html">
	* JMX Specification.</a>
	* @see <a href="package-summary.html#examples">
	* Ways to Access MXBeans</a>
	*
	* @author Mandy Chung
	* @since 1.5
	*/
	public interface MemoryPoolMXBean extends PlatformManagedObject {
	/**
	* Returns the name representing this memory pool.
	*
	* @return the name of this memory pool.
	*/
	public String getName();

	/**
	* Returns the type of this memory pool.
	*
	* <p>
	* <b>MBeanServer access</b>:<br>
	* The mapped type of <tt>MemoryType</tt> is <tt>String</tt>
	* and the value is the name of the <tt>MemoryType</tt>.
	*
	* @return the type of this memory pool.
	*/
	public MemoryType getType();

	/**
	* Returns an estimate of the memory usage of this memory pool.
	* This method returns <tt>null</tt>
	* if this memory pool is not valid (i.e. no longer exists).
	*
	* <p>
	* This method requests the Java virtual machine to make
	* a best-effort estimate of the current memory usage of this
	* memory pool. For some memory pools, this method may be an
	* expensive operation that requires some computation to determine
	* the estimate. An implementation should document when
	* this is the case.
	*
	* <p>This method is designed for use in monitoring system
	* memory usage and detecting low memory condition.
	*
	* <p>
	* <b>MBeanServer access</b>:<br>
	* The mapped type of <tt>MemoryUsage</tt> is
	* <tt>CompositeData</tt> with attributes as specified in
	* {@link MemoryUsage#from MemoryUsage}.
	*
	* @return a {@link MemoryUsage} object; or <tt>null</tt> if
	* this pool not valid.
	*/
	public MemoryUsage getUsage();

	/**
	* Returns the peak memory usage of this memory pool since the
	* Java virtual machine was started or since the peak was reset.
	* This method returns <tt>null</tt>
	* if this memory pool is not valid (i.e. no longer exists).
	*
	* <p>
	* <b>MBeanServer access</b>:<br>
	* The mapped type of <tt>MemoryUsage</tt> is
	* <tt>CompositeData</tt> with attributes as specified in
	* {@link MemoryUsage#from MemoryUsage}.
	*
	* @return a {@link MemoryUsage} object representing the peak
	* memory usage; or <tt>null</tt> if this pool is not valid.
	*
	*/
	public MemoryUsage getPeakUsage();

	/**
	* Resets the peak memory usage statistic of this memory pool
	* to the current memory usage.
	*
	* @throws java.lang.SecurityException if a security manager
	* exists and the caller does not have
	* ManagementPermission("control").
	*/
	public void resetPeakUsage();

	/**
	* Tests if this memory pool is valid in the Java virtual
	* machine. A memory pool becomes invalid once the Java virtual
	* machine removes it from the memory system.
	*
	* @return <tt>true</tt> if the memory pool is valid in the running
	* Java virtual machine;
	* <tt>false</tt> otherwise.
	*/
	public boolean isValid();

	/**
	* Returns the name of memory managers that manages this memory pool.
	* Each memory pool will be managed by at least one memory manager.
	*
	* @return an array of <tt>String</tt> objects, each is the name of
	* a memory manager managing this memory pool.
	*/
	public String[] getMemoryManagerNames();

	/**
	* Returns the usage threshold value of this memory pool in bytes.
	* Each memory pool has a platform-dependent default threshold value.
	* The current usage threshold can be changed via the
	* {@link #setUsageThreshold setUsageThreshold} method.
	*
	* @return the usage threshold value of this memory pool in bytes.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a usage threshold.
	*
	* @see #isUsageThresholdSupported
	*/
	public long getUsageThreshold();

	/**
	* Sets the threshold of this memory pool to the given <tt>threshold</tt>
	* value if this memory pool supports the usage threshold.
	* The usage threshold crossing checking is enabled in this memory pool
	* if the threshold is set to a positive value.
	* The usage threshold crossing checking is disabled
	* if it is set to zero.
	*
	* @param threshold the new threshold value in bytes. Must be non-negative.
	*
	* @throws IllegalArgumentException if <tt>threshold</tt> is negative
	* or greater than the maximum amount of memory for
	* this memory pool if defined.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a usage threshold.
	*
	* @throws java.lang.SecurityException if a security manager
	* exists and the caller does not have
	* ManagementPermission("control").
	*
	* @see #isUsageThresholdSupported
	* @see <a href="#UsageThreshold">Usage threshold</a>
	*/
	public void setUsageThreshold(long threshold);

	/**
	* Tests if the memory usage of this memory pool
	* reaches or exceeds its usage threshold value.
	*
	* @return <tt>true</tt> if the memory usage of
	* this memory pool reaches or exceeds the threshold value;
	* <tt>false</tt> otherwise.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a usage threshold.
	*/
	public boolean isUsageThresholdExceeded();

	/**
	* Returns the number of times that the memory usage has crossed
	* the usage threshold.
	*
	* @return the number of times that the memory usage
	* has crossed its usage threshold value.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a usage threshold.
	*/
	public long getUsageThresholdCount();

	/**
	* Tests if this memory pool supports usage threshold.
	*
	* @return <tt>true</tt> if this memory pool supports usage threshold;
	* <tt>false</tt> otherwise.
	*/
	public boolean isUsageThresholdSupported();

	/**
	* Returns the collection usage threshold value of this memory pool
	* in bytes. The default value is zero. The collection usage
	* threshold can be changed via the
	* {@link #setCollectionUsageThreshold setCollectionUsageThreshold} method.
	*
	* @return the collection usage threshold of this memory pool in bytes.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a collection usage threshold.
	*
	* @see #isCollectionUsageThresholdSupported
	*/
	public long getCollectionUsageThreshold();

	/**
	* Sets the collection usage threshold of this memory pool to
	* the given <tt>threshold</tt> value.
	* When this threshold is set to positive, the Java virtual machine
	* will check the memory usage at its best appropriate time after it has
	* expended effort in recycling unused objects in this memory pool.
	* <p>
	* The collection usage threshold crossing checking is enabled
	* in this memory pool if the threshold is set to a positive value.
	* The collection usage threshold crossing checking is disabled
	* if it is set to zero.
	*
	* @param threshold the new collection usage threshold value in bytes.
	* Must be non-negative.
	*
	* @throws IllegalArgumentException if <tt>threshold</tt> is negative
	* or greater than the maximum amount of memory for
	* this memory pool if defined.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a collection usage threshold.
	*
	* @throws java.lang.SecurityException if a security manager
	* exists and the caller does not have
	* ManagementPermission("control").
	*
	* @see #isCollectionUsageThresholdSupported
	* @see <a href="#CollectionThreshold">Collection usage threshold</a>
	*/
	public void setCollectionUsageThreshold(long threshold);

	/**
	* Tests if the memory usage of this memory pool after
	* the most recent collection on which the Java virtual
	* machine has expended effort has reached or
	* exceeded its collection usage threshold.
	* This method does not request the Java virtual
	* machine to perform any garbage collection other than its normal
	* automatic memory management.
	*
	* @return <tt>true</tt> if the memory usage of this memory pool
	* reaches or exceeds the collection usage threshold value
	* in the most recent collection;
	* <tt>false</tt> otherwise.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a usage threshold.
	*/
	public boolean isCollectionUsageThresholdExceeded();

	/**
	* Returns the number of times that the Java virtual machine
	* has detected that the memory usage has reached or
	* exceeded the collection usage threshold.
	*
	* @return the number of times that the memory
	* usage has reached or exceeded the collection usage threshold.
	*
	* @throws UnsupportedOperationException if this memory pool
	* does not support a collection usage threshold.
	*
	* @see #isCollectionUsageThresholdSupported
	*/
	public long getCollectionUsageThresholdCount();

	/**
	* Returns the memory usage after the Java virtual machine
	* most recently expended effort in recycling unused objects
	* in this memory pool.
	* This method does not request the Java virtual
	* machine to perform any garbage collection other than its normal
	* automatic memory management.
	* This method returns <tt>null</tt> if the Java virtual
	* machine does not support this method.
	*
	* <p>
	* <b>MBeanServer access</b>:<br>
	* The mapped type of <tt>MemoryUsage</tt> is
	* <tt>CompositeData</tt> with attributes as specified in
	* {@link MemoryUsage#from MemoryUsage}.
	*
	* @return a {@link MemoryUsage} representing the memory usage of
	* this memory pool after the Java virtual machine most recently
	* expended effort in recycling unused objects;
	* <tt>null</tt> if this method is not supported.
	*/
	public MemoryUsage getCollectionUsage();

	/**
	* Tests if this memory pool supports a collection usage threshold.
	*
	* @return <tt>true</tt> if this memory pool supports the
	* collection usage threshold; <tt>false</tt> otherwise.
	*/
	public boolean isCollectionUsageThresholdSupported();
	}

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