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src/java.management/share/classes/java/lang/management/ThreadMXBean.java

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 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  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package java.lang.management;
 27 
 28 import java.util.Map;
 29 
 30 /**
 31  * The management interface for the thread system of
 32  * the Java virtual machine.





 33  *
 34  * <p> A Java virtual machine has a single instance of the implementation
 35  * class of this interface.  This instance implementing this interface is
 36  * an <a href="ManagementFactory.html#MXBean">MXBean</a>
 37  * that can be obtained by calling
 38  * the {@link ManagementFactory#getThreadMXBean} method or
 39  * from the {@link ManagementFactory#getPlatformMBeanServer
 40  * platform MBeanServer} method.
 41  *
 42  * <p>The {@code ObjectName} for uniquely identifying the MXBean for
 43  * the thread system within an MBeanServer is:
 44  * <blockquote>
 45  *    {@link ManagementFactory#THREAD_MXBEAN_NAME
 46  *           java.lang:type=Threading}
 47  * </blockquote>
 48  *
 49  * It can be obtained by calling the
 50  * {@link PlatformManagedObject#getObjectName} method.
 51  *
 52  * <h2>Thread ID</h2>

106  * {@linkplain LockInfo <i>lock</i>} a thread is blocked to
107  * acquire or waiting on and which locks the thread currently owns.
108  * <p>
109  * The {@code ThreadMXBean} interface provides the
110  * {@link #findMonitorDeadlockedThreads} and
111  * {@link #findDeadlockedThreads} methods to find deadlocks in
112  * the running application.
113  *
114  * @see ManagementFactory#getPlatformMXBeans(Class)
115  * @see <a href="../../../javax/management/package-summary.html">
116  *      JMX Specification.</a>
117  * @see <a href="package-summary.html#examples">
118  *      Ways to Access MXBeans</a>
119  *
120  * @author  Mandy Chung
121  * @since   1.5
122  */
123 
124 public interface ThreadMXBean extends PlatformManagedObject {
125     /**
126      * Returns the current number of live threads including both
127      * daemon and non-daemon threads.

128      *
129      * @return the current number of live threads.
130      */
131     public int getThreadCount();
132 
133     /**
134      * Returns the peak live thread count since the Java virtual machine
135      * started or peak was reset.

136      *
137      * @return the peak live thread count.
138      */
139     public int getPeakThreadCount();
140 
141     /**
142      * Returns the total number of threads created and also started
143      * since the Java virtual machine started.

144      *
145      * @return the total number of threads started.
146      */
147     public long getTotalStartedThreadCount();
148 
149     /**
150      * Returns the current number of live daemon threads.

151      *
152      * @return the current number of live daemon threads.
153      */
154     public int getDaemonThreadCount();
155 
156     /**
157      * Returns all live thread IDs.

158      * Some threads included in the returned array
159      * may have been terminated when this method returns.
160      *
161      * @return an array of {@code long}, each is a thread ID.
162      *
163      * @throws SecurityException if a security manager
164      *         exists and the caller does not have
165      *         ManagementPermission("monitor").
166      */
167     public long[] getAllThreadIds();
168 
169     /**
170      * Returns the thread info for a thread of the specified
171      * {@code id} with no stack trace.
172      * This method is equivalent to calling:
173      * <blockquote>
174      *   {@link #getThreadInfo(long, int) getThreadInfo(id, 0);}
175      * </blockquote>
176      *
177      * <p>
178      * This method returns a {@code ThreadInfo} object representing
179      * the thread information for the thread of the specified ID.
180      * The stack trace, locked monitors, and locked synchronizers
181      * in the returned {@code ThreadInfo} object will
182      * be empty.
183      *
184      * If a thread of the given ID is not alive or does not exist,
185      * this method will return {@code null}.  A thread is alive if
186      * it has been started and has not yet died.
187      *
188      * <p>
189      * <b>MBeanServer access</b>:<br>
190      * The mapped type of {@code ThreadInfo} is
191      * {@code CompositeData} with attributes as specified in the
192      * {@link ThreadInfo#from ThreadInfo.from} method.
193      *
194      * @param id the thread ID of the thread. Must be positive.
195      *
196      * @return a {@link ThreadInfo} object for the thread of the given ID
197      * with no stack trace, no locked monitor and no synchronizer info;
198      * {@code null} if the thread of the given ID is not alive or
199      * it does not exist.
200      *
201      * @throws IllegalArgumentException if {@code id <= 0}.
202      * @throws SecurityException if a security manager
203      *         exists and the caller does not have
204      *         ManagementPermission("monitor").
205      */
206     public ThreadInfo getThreadInfo(long id);
207 
208     /**
209      * Returns the thread info for each thread
210      * whose ID is in the input array {@code ids} with no stack trace.
211      * This method is equivalent to calling:
212      * <blockquote><pre>
213      *   {@link #getThreadInfo(long[], int) getThreadInfo}(ids, 0);
214      * </pre></blockquote>
215      *
216      * <p>
217      * This method returns an array of the {@code ThreadInfo} objects.
218      * The stack trace, locked monitors, and locked synchronizers
219      * in each {@code ThreadInfo} object will be empty.
220      *
221      * If a thread of a given ID is not alive or does not exist,
222      * the corresponding element in the returned array will
223      * contain {@code null}.  A thread is alive if
224      * it has been started and has not yet died.
225      *
226      * <p>
227      * <b>MBeanServer access</b>:<br>
228      * The mapped type of {@code ThreadInfo} is
229      * {@code CompositeData} with attributes as specified in the
230      * {@link ThreadInfo#from ThreadInfo.from} method.
231      *
232      * @param ids an array of thread IDs.
233      * @return an array of the {@link ThreadInfo} objects, each containing
234      * information about a thread whose ID is in the corresponding
235      * element of the input array of IDs
236      * with no stack trace, no locked monitor and no synchronizer info.
237      *
238      * @throws IllegalArgumentException if any element in the input array
239      *         {@code ids} is {@code <= 0}.
240      * @throws SecurityException if a security manager
241      *         exists and the caller does not have
242      *         ManagementPermission("monitor").
243      */
244     public ThreadInfo[] getThreadInfo(long[] ids);
245 
246     /**
247      * Returns a thread info for a thread of the specified {@code id},
248      * with stack trace of a specified number of stack trace elements.
249      * The {@code maxDepth} parameter indicates the maximum number of
250      * {@link StackTraceElement} to be retrieved from the stack trace.
251      * If {@code maxDepth == Integer.MAX_VALUE}, the entire stack trace of
252      * the thread will be dumped.
253      * If {@code maxDepth == 0}, no stack trace of the thread
254      * will be dumped.
255      * This method does not obtain the locked monitors and locked
256      * synchronizers of the thread.
257      * <p>
258      * When the Java virtual machine has no stack trace information
259      * about a thread or {@code maxDepth == 0},
260      * the stack trace in the
261      * {@code ThreadInfo} object will be an empty array of
262      * {@code StackTraceElement}.
263      *
264      * <p>
265      * If a thread of the given ID is not alive or does not exist,
266      * this method will return {@code null}.  A thread is alive if
267      * it has been started and has not yet died.
268      *
269      * <p>
270      * <b>MBeanServer access</b>:<br>
271      * The mapped type of {@code ThreadInfo} is
272      * {@code CompositeData} with attributes as specified in the
273      * {@link ThreadInfo#from ThreadInfo.from} method.
274      *
275      * @param id the thread ID of the thread. Must be positive.
276      * @param maxDepth the maximum number of entries in the stack trace
277      * to be dumped. {@code Integer.MAX_VALUE} could be used to request
278      * the entire stack to be dumped.
279      *
280      * @return a {@link ThreadInfo} of the thread of the given ID
281      * with no locked monitor and synchronizer info.
282      * {@code null} if the thread of the given ID is not alive or
283      * it does not exist.
284      *
285      * @throws IllegalArgumentException if {@code id <= 0}.
286      * @throws IllegalArgumentException if {@code maxDepth is negative}.
287      * @throws SecurityException if a security manager
288      *         exists and the caller does not have
289      *         ManagementPermission("monitor").
290      *
291      */
292     public ThreadInfo getThreadInfo(long id, int maxDepth);
293 
294     /**
295      * Returns the thread info for each thread
296      * whose ID is in the input array {@code ids},
297      * with stack trace of a specified number of stack trace elements.
298      * The {@code maxDepth} parameter indicates the maximum number of
299      * {@link StackTraceElement} to be retrieved from the stack trace.
300      * If {@code maxDepth == Integer.MAX_VALUE}, the entire stack trace of
301      * the thread will be dumped.
302      * If {@code maxDepth == 0}, no stack trace of the thread
303      * will be dumped.
304      * This method does not obtain the locked monitors and locked
305      * synchronizers of the threads.
306      * <p>
307      * When the Java virtual machine has no stack trace information
308      * about a thread or {@code maxDepth == 0},
309      * the stack trace in the
310      * {@code ThreadInfo} object will be an empty array of
311      * {@code StackTraceElement}.
312      * <p>
313      * This method returns an array of the {@code ThreadInfo} objects,
314      * each is the thread information about the thread with the same index
315      * as in the {@code ids} array.
316      * If a thread of the given ID is not alive or does not exist,
317      * {@code null} will be set in the corresponding element
318      * in the returned array.  A thread is alive if
319      * it has been started and has not yet died.
320      *
321      * <p>
322      * <b>MBeanServer access</b>:<br>
323      * The mapped type of {@code ThreadInfo} is
324      * {@code CompositeData} with attributes as specified in the
325      * {@link ThreadInfo#from ThreadInfo.from} method.
326      *
327      * @param ids an array of thread IDs
328      * @param maxDepth the maximum number of entries in the stack trace
329      * to be dumped. {@code Integer.MAX_VALUE} could be used to request
330      * the entire stack to be dumped.
331      *
332      * @return an array of the {@link ThreadInfo} objects, each containing
333      * information about a thread whose ID is in the corresponding
334      * element of the input array of IDs with no locked monitor and
335      * synchronizer info.
336      *
337      * @throws IllegalArgumentException if {@code maxDepth is negative}.
338      * @throws IllegalArgumentException if any element in the input array
339      *      {@code ids} is {@code <= 0}.

433      * @throws UnsupportedOperationException if the Java
434      * virtual machine does not support CPU time measurement for
435      * the current thread.
436      *
437      * @see #getCurrentThreadCpuTime
438      * @see #isCurrentThreadCpuTimeSupported
439      * @see #isThreadCpuTimeEnabled
440      * @see #setThreadCpuTimeEnabled
441      */
442     public long getCurrentThreadUserTime();
443 
444     /**
445      * Returns the total CPU time for a thread of the specified ID in nanoseconds.
446      * The returned value is of nanoseconds precision but
447      * not necessarily nanoseconds accuracy.
448      * If the implementation distinguishes between user mode time and system
449      * mode time, the returned CPU time is the amount of time that
450      * the thread has executed in user mode or system mode.
451      *
452      * <p>
453      * If the thread of the specified ID is not alive or does not exist,
454      * this method returns {@code -1}. If CPU time measurement
455      * is disabled, this method returns {@code -1}.
456      * A thread is alive if it has been started and has not yet died.
457      * <p>
458      * If CPU time measurement is enabled after the thread has started,
459      * the Java virtual machine implementation may choose any time up to
460      * and including the time that the capability is enabled as the point
461      * where CPU time measurement starts.
462      *
463      * @param id the thread ID of a thread
464      * @return the total CPU time for a thread of the specified ID
465      * if the thread of the specified ID exists, the thread is alive,
466      * and CPU time measurement is enabled;
467      * {@code -1} otherwise.
468      *
469      * @throws IllegalArgumentException if {@code id <= 0}.
470      * @throws UnsupportedOperationException if the Java
471      * virtual machine does not support CPU time measurement for
472      * other threads.
473      *
474      * @see #getThreadUserTime
475      * @see #isThreadCpuTimeSupported
476      * @see #isThreadCpuTimeEnabled
477      * @see #setThreadCpuTimeEnabled
478      */
479     public long getThreadCpuTime(long id);
480 
481     /**
482      * Returns the CPU time that a thread of the specified ID
483      * has executed in user mode in nanoseconds.
484      * The returned value is of nanoseconds precision but
485      * not necessarily nanoseconds accuracy.
486      *
487      * <p>
488      * If the thread of the specified ID is not alive or does not exist,
489      * this method returns {@code -1}. If CPU time measurement
490      * is disabled, this method returns {@code -1}.
491      * A thread is alive if it has been started and has not yet died.
492      * <p>
493      * If CPU time measurement is enabled after the thread has started,
494      * the Java virtual machine implementation may choose any time up to
495      * and including the time that the capability is enabled as the point
496      * where CPU time measurement starts.
497      *
498      * @param id the thread ID of a thread
499      * @return the user-level CPU time for a thread of the specified ID
500      * if the thread of the specified ID exists, the thread is alive,
501      * and CPU time measurement is enabled;
502      * {@code -1} otherwise.
503      *
504      * @throws IllegalArgumentException if {@code id <= 0}.
505      * @throws UnsupportedOperationException if the Java
506      * virtual machine does not support CPU time measurement for
507      * other threads.
508      *
509      * @see #getThreadCpuTime
510      * @see #isThreadCpuTimeSupported
511      * @see #isThreadCpuTimeEnabled

577      */
578     public void setThreadCpuTimeEnabled(boolean enable);
579 
580     /**
581      * Finds cycles of threads that are in deadlock waiting to acquire
582      * object monitors. That is, threads that are blocked waiting to enter a
583      * synchronization block or waiting to reenter a synchronization block
584      * after an {@link Object#wait Object.wait} call,
585      * where each thread owns one monitor while
586      * trying to obtain another monitor already held by another thread
587      * in a cycle.
588      * <p>
589      * More formally, a thread is <em>monitor deadlocked</em> if it is
590      * part of a cycle in the relation "is waiting for an object monitor
591      * owned by".  In the simplest case, thread A is blocked waiting
592      * for a monitor owned by thread B, and thread B is blocked waiting
593      * for a monitor owned by thread A.
594      * <p>
595      * This method is designed for troubleshooting use, but not for
596      * synchronization control.  It might be an expensive operation.


597      * <p>
598      * This method finds deadlocks involving only object monitors.
599      * To find deadlocks involving both object monitors and
600      * <a href="LockInfo.html#OwnableSynchronizer">ownable synchronizers</a>,
601      * the {@link #findDeadlockedThreads findDeadlockedThreads} method
602      * should be used.
603      *
604      * @return an array of IDs of the threads that are monitor
605      * deadlocked, if any; {@code null} otherwise.
606      *
607      * @throws SecurityException if a security manager
608      *         exists and the caller does not have
609      *         ManagementPermission("monitor").
610      *
611      * @see #findDeadlockedThreads
612      */
613     public long[] findMonitorDeadlockedThreads();
614 
615     /**
616      * Resets the peak thread count to the current number of

620      *         exists and the caller does not have
621      *         ManagementPermission("control").
622      *
623      * @see #getPeakThreadCount
624      * @see #getThreadCount
625      */
626     public void resetPeakThreadCount();
627 
628     /**
629      * Finds cycles of threads that are in deadlock waiting to acquire
630      * object monitors or
631      * <a href="LockInfo.html#OwnableSynchronizer">ownable synchronizers</a>.
632      *
633      * Threads are <em>deadlocked</em> in a cycle waiting for a lock of
634      * these two types if each thread owns one lock while
635      * trying to acquire another lock already held
636      * by another thread in the cycle.
637      * <p>
638      * This method is designed for troubleshooting use, but not for
639      * synchronization control.  It might be an expensive operation.


640      *
641      * @return an array of IDs of the threads that are
642      * deadlocked waiting for object monitors or ownable synchronizers, if any;
643      * {@code null} otherwise.
644      *
645      * @throws SecurityException if a security manager
646      *         exists and the caller does not have
647      *         ManagementPermission("monitor").
648      * @throws UnsupportedOperationException if the Java virtual
649      * machine does not support monitoring of ownable synchronizer usage.
650      *
651      * @see #isSynchronizerUsageSupported
652      * @see #findMonitorDeadlockedThreads
653      * @since 1.6
654      */
655     public long[] findDeadlockedThreads();
656 
657     /**
658      * Tests if the Java virtual machine supports monitoring of
659      * object monitor usage.

733      * with stack trace of the specified maximum number of elements
734      * and synchronization information.
735      * If {@code maxDepth == 0}, no stack trace of the thread
736      * will be dumped.
737      *
738      * <p>
739      * This method obtains a snapshot of the thread information
740      * for each thread including:
741      * <ul>
742      *    <li>stack trace of the specified maximum number of elements,</li>
743      *    <li>the object monitors currently locked by the thread
744      *        if {@code lockedMonitors} is {@code true}, and</li>
745      *    <li>the <a href="LockInfo.html#OwnableSynchronizer">
746      *        ownable synchronizers</a> currently locked by the thread
747      *        if {@code lockedSynchronizers} is {@code true}.</li>
748      * </ul>
749      * <p>
750      * This method returns an array of the {@code ThreadInfo} objects,
751      * each is the thread information about the thread with the same index
752      * as in the {@code ids} array.
753      * If a thread of the given ID is not alive or does not exist,
754      * {@code null} will be set in the corresponding element
755      * in the returned array.  A thread is alive if
756      * it has been started and has not yet died.
757      * <p>
758      * If a thread does not lock any object monitor or {@code lockedMonitors}
759      * is {@code false}, the returned {@code ThreadInfo} object will have an
760      * empty {@code MonitorInfo} array.  Similarly, if a thread does not
761      * lock any synchronizer or {@code lockedSynchronizers} is {@code false},
762      * the returned {@code ThreadInfo} object
763      * will have an empty {@code LockInfo} array.
764      *
765      * <p>
766      * When both {@code lockedMonitors} and {@code lockedSynchronizers}
767      * parameters are {@code false}, it is equivalent to calling:
768      * <blockquote><pre>
769      *     {@link #getThreadInfo(long[], int)  getThreadInfo(ids, maxDepth)}
770      * </pre></blockquote>
771      *
772      * <p>
773      * This method is designed for troubleshooting use, but not for
774      * synchronization control.  It might be an expensive operation.
775      *
776      * <p>

806      *           <li>if {@code lockedSynchronizers} is {@code true} but
807      *               the Java virtual machine does not support monitoring
808      *               of {@linkplain #isSynchronizerUsageSupported
809      *               ownable synchronizer usage}.</li>
810      *         </ul>
811      *
812      * @see #isObjectMonitorUsageSupported
813      * @see #isSynchronizerUsageSupported
814      *
815      * @since 10
816      */
817 
818     public default ThreadInfo[] getThreadInfo(long[] ids, boolean lockedMonitors,
819                                               boolean lockedSynchronizers, int maxDepth) {
820         throw new UnsupportedOperationException();
821     }
822 
823     /**
824      * Returns the thread info for all live threads with stack trace
825      * and synchronization information.
826      * This is equivalent to calling:

827      * <blockquote>
828      * {@link #dumpAllThreads(boolean, boolean, int)
829      * dumpAllThreads(lockedMonitors, lockedSynchronizers, Integer.MAX_VALUE)}
830      * </blockquote>
831      *
832      * @param  lockedMonitors if {@code true}, dump all locked monitors.
833      * @param  lockedSynchronizers if {@code true}, dump all locked
834      *             ownable synchronizers.
835      *
836      * @return an array of {@link ThreadInfo} for all live threads.
837      *
838      * @throws SecurityException if a security manager
839      *         exists and the caller does not have
840      *         ManagementPermission("monitor").
841      * @throws UnsupportedOperationException
842      *         <ul>
843      *           <li>if {@code lockedMonitors} is {@code true} but
844      *               the Java virtual machine does not support monitoring
845      *               of {@linkplain #isObjectMonitorUsageSupported
846      *               object monitor usage}; or</li>
847      *           <li>if {@code lockedSynchronizers} is {@code true} but
848      *               the Java virtual machine does not support monitoring
849      *               of {@linkplain #isSynchronizerUsageSupported
850      *               ownable synchronizer usage}.</li>
851      *         </ul>
852      *
853      * @see #isObjectMonitorUsageSupported
854      * @see #isSynchronizerUsageSupported
855      *
856      * @since 1.6
857      */
858     public ThreadInfo[] dumpAllThreads(boolean lockedMonitors, boolean lockedSynchronizers);
859 
860 
861     /**
862      * Returns the thread info for all live threads
863      * with stack trace of the specified maximum number of elements
864      * and synchronization information.
865      * if {@code maxDepth == 0}, no stack trace of the thread
866      * will be dumped.

867      * Some threads included in the returned array
868      * may have been terminated when this method returns.
869      *
870      * <p>
871      * This method returns an array of {@link ThreadInfo} objects
872      * as specified in the {@link #getThreadInfo(long[], boolean, boolean, int)}
873      * method.
874      *
875      * @implSpec The default implementation throws
876      * {@code UnsupportedOperationException}.
877      *
878      * @param  lockedMonitors if {@code true}, dump all locked monitors.
879      * @param  lockedSynchronizers if {@code true}, dump all locked
880      *             ownable synchronizers.
881      * @param  maxDepth indicates the maximum number of
882      * {@link StackTraceElement} to be retrieved from the stack trace.
883      *
884      * @return an array of {@link ThreadInfo} for all live threads.
885      *
886      * @throws IllegalArgumentException if {@code maxDepth} is negative.

 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  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package java.lang.management;
 27 
 28 import java.util.Map;
 29 
 30 /**
 31  * The management interface for the thread system of the Java virtual machine.
 32  *
 33  * <p> {@code ThreadMXBean} supports monitoring and management of <em>live
 34  * platform threads</em> in the Java virtual machine. Platform threads are
 35  * typically mapped to kernel threads scheduled by the operating system.
 36  * {@code ThreadMXBean} does not support monitoring or management of {@linkplain
 37  * Thread#isVirtual() virtual threads}.
 38  *
 39  * <p> A Java virtual machine has a single instance of the implementation
 40  * class of this interface.  This instance implementing this interface is
 41  * an <a href="ManagementFactory.html#MXBean">MXBean</a>
 42  * that can be obtained by calling
 43  * the {@link ManagementFactory#getThreadMXBean} method or
 44  * from the {@link ManagementFactory#getPlatformMBeanServer
 45  * platform MBeanServer} method.
 46  *
 47  * <p>The {@code ObjectName} for uniquely identifying the MXBean for
 48  * the thread system within an MBeanServer is:
 49  * <blockquote>
 50  *    {@link ManagementFactory#THREAD_MXBEAN_NAME
 51  *           java.lang:type=Threading}
 52  * </blockquote>
 53  *
 54  * It can be obtained by calling the
 55  * {@link PlatformManagedObject#getObjectName} method.
 56  *
 57  * <h2>Thread ID</h2>

111  * {@linkplain LockInfo <i>lock</i>} a thread is blocked to
112  * acquire or waiting on and which locks the thread currently owns.
113  * <p>
114  * The {@code ThreadMXBean} interface provides the
115  * {@link #findMonitorDeadlockedThreads} and
116  * {@link #findDeadlockedThreads} methods to find deadlocks in
117  * the running application.
118  *
119  * @see ManagementFactory#getPlatformMXBeans(Class)
120  * @see <a href="../../../javax/management/package-summary.html">
121  *      JMX Specification.</a>
122  * @see <a href="package-summary.html#examples">
123  *      Ways to Access MXBeans</a>
124  *
125  * @author  Mandy Chung
126  * @since   1.5
127  */
128 
129 public interface ThreadMXBean extends PlatformManagedObject {
130     /**
131      * Returns the current number of live platform threads including both
132      * daemon and non-daemon threads.
133      * The count does not include virtual threads.
134      *
135      * @return the current number of live platform threads.
136      */
137     public int getThreadCount();
138 
139     /**
140      * Returns the peak live platform thread count since the Java virtual
141      * machine started or peak was reset.
142      * The count does not include virtual threads.
143      *
144      * @return the peak live platform thread count.
145      */
146     public int getPeakThreadCount();
147 
148     /**
149      * Returns the total number of platform threads created and also started
150      * since the Java virtual machine started.
151      * The count does not include virtual threads.
152      *
153      * @return the total number of platform threads started.
154      */
155     public long getTotalStartedThreadCount();
156 
157     /**
158      * Returns the current number of live platform threads that are daemon threads.
159      * The count does not include virtual threads.
160      *
161      * @return the current number of live platform threads that are daemon threads.
162      */
163     public int getDaemonThreadCount();
164 
165     /**
166      * Returns the threadIDs of all live platform threads.
167      * The thread IDs of virtual threads are not included.
168      * Some threads included in the returned array
169      * may have been terminated when this method returns.
170      *
171      * @return an array of {@code long}, each is a thread ID.
172      *
173      * @throws SecurityException if a security manager
174      *         exists and the caller does not have
175      *         ManagementPermission("monitor").
176      */
177     public long[] getAllThreadIds();
178 
179     /**
180      * Returns the thread info for a thread of the specified
181      * {@code id} with no stack trace.
182      * This method is equivalent to calling:
183      * <blockquote>
184      *   {@link #getThreadInfo(long, int) getThreadInfo(id, 0);}
185      * </blockquote>
186      *
187      * <p>
188      * This method returns a {@code ThreadInfo} object representing
189      * the thread information for the thread of the specified ID.
190      * The stack trace, locked monitors, and locked synchronizers
191      * in the returned {@code ThreadInfo} object will
192      * be empty.
193      *
194      * If a thread of the given ID is a virtual thread, is not alive, or does
195      * not exist, then this method will return {@code null}. A thread is
196      * alive if it has been started and has not yet terminated.
197      *
198      * <p>
199      * <b>MBeanServer access</b>:<br>
200      * The mapped type of {@code ThreadInfo} is
201      * {@code CompositeData} with attributes as specified in the
202      * {@link ThreadInfo#from ThreadInfo.from} method.
203      *
204      * @param id the thread ID of the thread. Must be positive.
205      *
206      * @return a {@link ThreadInfo} object for the thread of the given ID
207      * with no stack trace, no locked monitor and no synchronizer info;
208      * {@code null} if the thread of the given ID is a virtual thread,
209      * is not alive, or it does not exist.
210      *
211      * @throws IllegalArgumentException if {@code id <= 0}.
212      * @throws SecurityException if a security manager
213      *         exists and the caller does not have
214      *         ManagementPermission("monitor").
215      */
216     public ThreadInfo getThreadInfo(long id);
217 
218     /**
219      * Returns the thread info for each thread
220      * whose ID is in the input array {@code ids} with no stack trace.
221      * This method is equivalent to calling:
222      * <blockquote><pre>
223      *   {@link #getThreadInfo(long[], int) getThreadInfo}(ids, 0);
224      * </pre></blockquote>
225      *
226      * <p>
227      * This method returns an array of the {@code ThreadInfo} objects.
228      * The stack trace, locked monitors, and locked synchronizers
229      * in each {@code ThreadInfo} object will be empty.
230      *
231      * If a thread of the given ID is a virtual thread, is not alive, or does
232      * not exist, the corresponding element in the returned array will
233      * contain {@code null}.  A thread is alive if
234      * it has been started and has not yet terminated.
235      *
236      * <p>
237      * <b>MBeanServer access</b>:<br>
238      * The mapped type of {@code ThreadInfo} is
239      * {@code CompositeData} with attributes as specified in the
240      * {@link ThreadInfo#from ThreadInfo.from} method.
241      *
242      * @param ids an array of thread IDs.
243      * @return an array of the {@link ThreadInfo} objects, each containing
244      * information about a thread whose ID is in the corresponding
245      * element of the input array of IDs
246      * with no stack trace, no locked monitor and no synchronizer info.
247      *
248      * @throws IllegalArgumentException if any element in the input array
249      *         {@code ids} is {@code <= 0}.
250      * @throws SecurityException if a security manager
251      *         exists and the caller does not have
252      *         ManagementPermission("monitor").
253      */
254     public ThreadInfo[] getThreadInfo(long[] ids);
255 
256     /**
257      * Returns a thread info for a thread of the specified {@code id},
258      * with stack trace of a specified number of stack trace elements.
259      * The {@code maxDepth} parameter indicates the maximum number of
260      * {@link StackTraceElement} to be retrieved from the stack trace.
261      * If {@code maxDepth == Integer.MAX_VALUE}, the entire stack trace of
262      * the thread will be dumped.
263      * If {@code maxDepth == 0}, no stack trace of the thread
264      * will be dumped.
265      * This method does not obtain the locked monitors and locked
266      * synchronizers of the thread.
267      * <p>
268      * When the Java virtual machine has no stack trace information
269      * about a thread or {@code maxDepth == 0},
270      * the stack trace in the
271      * {@code ThreadInfo} object will be an empty array of
272      * {@code StackTraceElement}.
273      *
274      * <p>
275      * If a thread of the given ID is a virtual thread, is not alive, or does
276      * not exist, this method will return {@code null}. A thread is alive if
277      * it has been started and has not yet terminated.
278      *
279      * <p>
280      * <b>MBeanServer access</b>:<br>
281      * The mapped type of {@code ThreadInfo} is
282      * {@code CompositeData} with attributes as specified in the
283      * {@link ThreadInfo#from ThreadInfo.from} method.
284      *
285      * @param id the thread ID of the thread. Must be positive.
286      * @param maxDepth the maximum number of entries in the stack trace
287      * to be dumped. {@code Integer.MAX_VALUE} could be used to request
288      * the entire stack to be dumped.
289      *
290      * @return a {@link ThreadInfo} of the thread of the given ID
291      * with no locked monitor and synchronizer info.
292      * {@code null} if the thread of the given ID is a virtual thread, is
293      * not alive or it does not exist.
294      *
295      * @throws IllegalArgumentException if {@code id <= 0}.
296      * @throws IllegalArgumentException if {@code maxDepth is negative}.
297      * @throws SecurityException if a security manager
298      *         exists and the caller does not have
299      *         ManagementPermission("monitor").
300      *
301      */
302     public ThreadInfo getThreadInfo(long id, int maxDepth);
303 
304     /**
305      * Returns the thread info for each thread
306      * whose ID is in the input array {@code ids},
307      * with stack trace of a specified number of stack trace elements.
308      * The {@code maxDepth} parameter indicates the maximum number of
309      * {@link StackTraceElement} to be retrieved from the stack trace.
310      * If {@code maxDepth == Integer.MAX_VALUE}, the entire stack trace of
311      * the thread will be dumped.
312      * If {@code maxDepth == 0}, no stack trace of the thread
313      * will be dumped.
314      * This method does not obtain the locked monitors and locked
315      * synchronizers of the threads.
316      * <p>
317      * When the Java virtual machine has no stack trace information
318      * about a thread or {@code maxDepth == 0},
319      * the stack trace in the
320      * {@code ThreadInfo} object will be an empty array of
321      * {@code StackTraceElement}.
322      * <p>
323      * This method returns an array of the {@code ThreadInfo} objects,
324      * each is the thread information about the thread with the same index
325      * as in the {@code ids} array.
326      * If a thread of the given ID is a virtual thread, is not alive, or does
327      * not exist, {@code null} will be set in the corresponding element
328      * in the returned array.  A thread is alive if
329      * it has been started and has not yet terminated.
330      *
331      * <p>
332      * <b>MBeanServer access</b>:<br>
333      * The mapped type of {@code ThreadInfo} is
334      * {@code CompositeData} with attributes as specified in the
335      * {@link ThreadInfo#from ThreadInfo.from} method.
336      *
337      * @param ids an array of thread IDs
338      * @param maxDepth the maximum number of entries in the stack trace
339      * to be dumped. {@code Integer.MAX_VALUE} could be used to request
340      * the entire stack to be dumped.
341      *
342      * @return an array of the {@link ThreadInfo} objects, each containing
343      * information about a thread whose ID is in the corresponding
344      * element of the input array of IDs with no locked monitor and
345      * synchronizer info.
346      *
347      * @throws IllegalArgumentException if {@code maxDepth is negative}.
348      * @throws IllegalArgumentException if any element in the input array
349      *      {@code ids} is {@code <= 0}.

443      * @throws UnsupportedOperationException if the Java
444      * virtual machine does not support CPU time measurement for
445      * the current thread.
446      *
447      * @see #getCurrentThreadCpuTime
448      * @see #isCurrentThreadCpuTimeSupported
449      * @see #isThreadCpuTimeEnabled
450      * @see #setThreadCpuTimeEnabled
451      */
452     public long getCurrentThreadUserTime();
453 
454     /**
455      * Returns the total CPU time for a thread of the specified ID in nanoseconds.
456      * The returned value is of nanoseconds precision but
457      * not necessarily nanoseconds accuracy.
458      * If the implementation distinguishes between user mode time and system
459      * mode time, the returned CPU time is the amount of time that
460      * the thread has executed in user mode or system mode.
461      *
462      * <p>
463      * If the thread of the specified ID is a virtual thread, is not alive or
464      * does not exist, this method returns {@code -1}. If CPU time measurement
465      * is disabled, this method returns {@code -1}.
466      * A thread is alive if it has been started and has not yet terminated.
467      * <p>
468      * If CPU time measurement is enabled after the thread has started,
469      * the Java virtual machine implementation may choose any time up to
470      * and including the time that the capability is enabled as the point
471      * where CPU time measurement starts.
472      *
473      * @param id the thread ID of a thread
474      * @return the total CPU time for a thread of the specified ID
475      * if the thread of the specified ID exists, the thread is alive,
476      * and CPU time measurement is enabled;
477      * {@code -1} otherwise.
478      *
479      * @throws IllegalArgumentException if {@code id <= 0}.
480      * @throws UnsupportedOperationException if the Java
481      * virtual machine does not support CPU time measurement for
482      * other threads.
483      *
484      * @see #getThreadUserTime
485      * @see #isThreadCpuTimeSupported
486      * @see #isThreadCpuTimeEnabled
487      * @see #setThreadCpuTimeEnabled
488      */
489     public long getThreadCpuTime(long id);
490 
491     /**
492      * Returns the CPU time that a thread of the specified ID
493      * has executed in user mode in nanoseconds.
494      * The returned value is of nanoseconds precision but
495      * not necessarily nanoseconds accuracy.
496      *
497      * <p>
498      * If the thread of the specified ID is a virtual thread, is not alive, or
499      * does not exist, this method returns {@code -1}. If CPU time measurement
500      * is disabled, this method returns {@code -1}.
501      * A thread is alive if it has been started and has not yet terminated.
502      * <p>
503      * If CPU time measurement is enabled after the thread has started,
504      * the Java virtual machine implementation may choose any time up to
505      * and including the time that the capability is enabled as the point
506      * where CPU time measurement starts.
507      *
508      * @param id the thread ID of a thread
509      * @return the user-level CPU time for a thread of the specified ID
510      * if the thread of the specified ID exists, the thread is alive,
511      * and CPU time measurement is enabled;
512      * {@code -1} otherwise.
513      *
514      * @throws IllegalArgumentException if {@code id <= 0}.
515      * @throws UnsupportedOperationException if the Java
516      * virtual machine does not support CPU time measurement for
517      * other threads.
518      *
519      * @see #getThreadCpuTime
520      * @see #isThreadCpuTimeSupported
521      * @see #isThreadCpuTimeEnabled

587      */
588     public void setThreadCpuTimeEnabled(boolean enable);
589 
590     /**
591      * Finds cycles of threads that are in deadlock waiting to acquire
592      * object monitors. That is, threads that are blocked waiting to enter a
593      * synchronization block or waiting to reenter a synchronization block
594      * after an {@link Object#wait Object.wait} call,
595      * where each thread owns one monitor while
596      * trying to obtain another monitor already held by another thread
597      * in a cycle.
598      * <p>
599      * More formally, a thread is <em>monitor deadlocked</em> if it is
600      * part of a cycle in the relation "is waiting for an object monitor
601      * owned by".  In the simplest case, thread A is blocked waiting
602      * for a monitor owned by thread B, and thread B is blocked waiting
603      * for a monitor owned by thread A.
604      * <p>
605      * This method is designed for troubleshooting use, but not for
606      * synchronization control.  It might be an expensive operation.
607      * Its behavior with cycles involving virtual threads is not defined
608      * in this release.
609      * <p>
610      * This method finds deadlocks involving only object monitors.
611      * To find deadlocks involving both object monitors and
612      * <a href="LockInfo.html#OwnableSynchronizer">ownable synchronizers</a>,
613      * the {@link #findDeadlockedThreads findDeadlockedThreads} method
614      * should be used.
615      *
616      * @return an array of IDs of the threads that are monitor
617      * deadlocked, if any; {@code null} otherwise.
618      *
619      * @throws SecurityException if a security manager
620      *         exists and the caller does not have
621      *         ManagementPermission("monitor").
622      *
623      * @see #findDeadlockedThreads
624      */
625     public long[] findMonitorDeadlockedThreads();
626 
627     /**
628      * Resets the peak thread count to the current number of

632      *         exists and the caller does not have
633      *         ManagementPermission("control").
634      *
635      * @see #getPeakThreadCount
636      * @see #getThreadCount
637      */
638     public void resetPeakThreadCount();
639 
640     /**
641      * Finds cycles of threads that are in deadlock waiting to acquire
642      * object monitors or
643      * <a href="LockInfo.html#OwnableSynchronizer">ownable synchronizers</a>.
644      *
645      * Threads are <em>deadlocked</em> in a cycle waiting for a lock of
646      * these two types if each thread owns one lock while
647      * trying to acquire another lock already held
648      * by another thread in the cycle.
649      * <p>
650      * This method is designed for troubleshooting use, but not for
651      * synchronization control.  It might be an expensive operation.
652      * Its behavior with cycles involving virtual threads is not defined
653      * in this release.
654      *
655      * @return an array of IDs of the threads that are
656      * deadlocked waiting for object monitors or ownable synchronizers, if any;
657      * {@code null} otherwise.
658      *
659      * @throws SecurityException if a security manager
660      *         exists and the caller does not have
661      *         ManagementPermission("monitor").
662      * @throws UnsupportedOperationException if the Java virtual
663      * machine does not support monitoring of ownable synchronizer usage.
664      *
665      * @see #isSynchronizerUsageSupported
666      * @see #findMonitorDeadlockedThreads
667      * @since 1.6
668      */
669     public long[] findDeadlockedThreads();
670 
671     /**
672      * Tests if the Java virtual machine supports monitoring of
673      * object monitor usage.

747      * with stack trace of the specified maximum number of elements
748      * and synchronization information.
749      * If {@code maxDepth == 0}, no stack trace of the thread
750      * will be dumped.
751      *
752      * <p>
753      * This method obtains a snapshot of the thread information
754      * for each thread including:
755      * <ul>
756      *    <li>stack trace of the specified maximum number of elements,</li>
757      *    <li>the object monitors currently locked by the thread
758      *        if {@code lockedMonitors} is {@code true}, and</li>
759      *    <li>the <a href="LockInfo.html#OwnableSynchronizer">
760      *        ownable synchronizers</a> currently locked by the thread
761      *        if {@code lockedSynchronizers} is {@code true}.</li>
762      * </ul>
763      * <p>
764      * This method returns an array of the {@code ThreadInfo} objects,
765      * each is the thread information about the thread with the same index
766      * as in the {@code ids} array.
767      * If a thread of the given ID is a virtual thread, is not alive, or does
768      * not exist, {@code null} will be set in the corresponding element
769      * in the returned array.  A thread is alive if
770      * it has been started and has not yet terminated.
771      * <p>
772      * If a thread does not lock any object monitor or {@code lockedMonitors}
773      * is {@code false}, the returned {@code ThreadInfo} object will have an
774      * empty {@code MonitorInfo} array.  Similarly, if a thread does not
775      * lock any synchronizer or {@code lockedSynchronizers} is {@code false},
776      * the returned {@code ThreadInfo} object
777      * will have an empty {@code LockInfo} array.
778      *
779      * <p>
780      * When both {@code lockedMonitors} and {@code lockedSynchronizers}
781      * parameters are {@code false}, it is equivalent to calling:
782      * <blockquote><pre>
783      *     {@link #getThreadInfo(long[], int)  getThreadInfo(ids, maxDepth)}
784      * </pre></blockquote>
785      *
786      * <p>
787      * This method is designed for troubleshooting use, but not for
788      * synchronization control.  It might be an expensive operation.
789      *
790      * <p>

820      *           <li>if {@code lockedSynchronizers} is {@code true} but
821      *               the Java virtual machine does not support monitoring
822      *               of {@linkplain #isSynchronizerUsageSupported
823      *               ownable synchronizer usage}.</li>
824      *         </ul>
825      *
826      * @see #isObjectMonitorUsageSupported
827      * @see #isSynchronizerUsageSupported
828      *
829      * @since 10
830      */
831 
832     public default ThreadInfo[] getThreadInfo(long[] ids, boolean lockedMonitors,
833                                               boolean lockedSynchronizers, int maxDepth) {
834         throw new UnsupportedOperationException();
835     }
836 
837     /**
838      * Returns the thread info for all live threads with stack trace
839      * and synchronization information.
840      * The thread IDs of virtual threads are not included.
841      * This method is equivalent to calling:
842      * <blockquote>
843      * {@link #dumpAllThreads(boolean, boolean, int)
844      * dumpAllThreads(lockedMonitors, lockedSynchronizers, Integer.MAX_VALUE)}
845      * </blockquote>
846      *
847      * @param  lockedMonitors if {@code true}, dump all locked monitors.
848      * @param  lockedSynchronizers if {@code true}, dump all locked
849      *             ownable synchronizers.
850      *
851      * @return an array of {@link ThreadInfo} for all live threads.
852      *
853      * @throws SecurityException if a security manager
854      *         exists and the caller does not have
855      *         ManagementPermission("monitor").
856      * @throws UnsupportedOperationException
857      *         <ul>
858      *           <li>if {@code lockedMonitors} is {@code true} but
859      *               the Java virtual machine does not support monitoring
860      *               of {@linkplain #isObjectMonitorUsageSupported
861      *               object monitor usage}; or</li>
862      *           <li>if {@code lockedSynchronizers} is {@code true} but
863      *               the Java virtual machine does not support monitoring
864      *               of {@linkplain #isSynchronizerUsageSupported
865      *               ownable synchronizer usage}.</li>
866      *         </ul>
867      *
868      * @see #isObjectMonitorUsageSupported
869      * @see #isSynchronizerUsageSupported
870      *
871      * @since 1.6
872      */
873     public ThreadInfo[] dumpAllThreads(boolean lockedMonitors, boolean lockedSynchronizers);
874 
875 
876     /**
877      * Returns the thread info for all live threads
878      * with stack trace of the specified maximum number of elements
879      * and synchronization information.
880      * if {@code maxDepth == 0}, no stack trace of the thread
881      * will be dumped.
882      * The thread IDs of virtual threads are not included.
883      * Some threads included in the returned array
884      * may have been terminated when this method returns.
885      *
886      * <p>
887      * This method returns an array of {@link ThreadInfo} objects
888      * as specified in the {@link #getThreadInfo(long[], boolean, boolean, int)}
889      * method.
890      *
891      * @implSpec The default implementation throws
892      * {@code UnsupportedOperationException}.
893      *
894      * @param  lockedMonitors if {@code true}, dump all locked monitors.
895      * @param  lockedSynchronizers if {@code true}, dump all locked
896      *             ownable synchronizers.
897      * @param  maxDepth indicates the maximum number of
898      * {@link StackTraceElement} to be retrieved from the stack trace.
899      *
900      * @return an array of {@link ThreadInfo} for all live threads.
901      *
902      * @throws IllegalArgumentException if {@code maxDepth} is negative.
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