Interface ThreadMXBean

This method returns information on all live threads at the time of execution (some threads may have terminated by the time the method completes). This method is simply a shorthand for calling {@link #getThreadInfo(long[], boolean, boolean)} with the return value of {@link #getAllThreadIds()}.

Parameters: lockedMonitors true if the returned {@link ThreadInfo} objects should contain information on locked monitors. lockedSynchronizers true if the returned {@link ThreadInfo} objects should contain information on locked ownable synchronizers.

Returns: an array of {@link ThreadInfo} objects for all live threads.

Throws: SecurityException if a security manager exists and denies ManagementPermission("monitor"). UnsupportedOperationException if lockedMonitors is true, but object monitor usage monitoring is not supported by the VM, or lockedSynchronizers is true, but ownable synchronizer usage monitoring is not supported by the VM.

Since: 1.6

See Also: (long[], boolean, boolean) getAllThreadIds isObjectMonitorUsageSupported isSynchronizerUsageSupported

This method obtains a list of threads which are deadlocked waiting to obtain monitor or ownable synchronizer ownership. This is similar to the behaviour described for {@link #getMonitorDeadlockedThreads()}, except this method also takes in to account deadlocks involving ownable synchronizers.

Note that this method is not designed for controlling synchronization, but for troubleshooting problems which cause such deadlocks; it may be prohibitively expensive to use in normal operation. If only deadlocks involving monitors are of interest, then {@link #findMonitorDeadlockedThreads()} should be used in preference to this method.

Returns: an array of thread identifiers, corresponding to threads which are currently in a deadlocked situation, or null if there are no deadlocks.

Throws: SecurityException if a security manager exists and denies ManagementPermission("monitor"). UnsupportedOperationException if the VM does not support the monitoring of ownable synchronizer usage.

Since: 1.6

See Also: findMonitorDeadlockedThreads isSynchronizerUsageSupported

This method obtains a list of threads which are deadlocked waiting to obtain monitor ownership. On entering a synchronized method of an object, or re-entering it after returning from an {@link java.lang.Object#wait()} call, a thread obtains ownership of the object's monitor.

Deadlocks can occur in this situation if one or more threads end up waiting for a monitor, P, while also retaining ownership of a monitor, Q, required by the thread that currently owns P. To give a simple example, imagine thread A calls a synchronized method, R, obtaining the monitor, P. It then sleeps within that method, allowing thread B to run, but still retaining ownership of P. B calls another synchronized method, S, which causes it to obtain the monitor, Q, of a different object. While in that method, it then wants to call the original synchronized method, R, called by A. Doing so requires ownership of P, which is still held by A. Hence, it becomes blocked.

A then finishes its sleep, becomes runnable, and is then allowed to run, being the only eligible thread in this scenario. A tries to call the synchronized method, S. It also gets blocked, because B still holds the monitor, Q. Hence, the two threads, A and B, are deadlocked, as neither can give up its monitor without first obtaining the monitor held by the other thread.

Calling this method in this scenario would return the thread IDs of A and B. Note that this method is not designed for controlling synchronization, but for troubleshooting problems which cause such deadlocks; it may be prohibitively expensive to use in normal operation. This method only returns deadlocks involving monitors; to include deadlocks involving ownable synchronizers, {@link #findDeadlockedThreads()} should be used instead.

Returns: an array of thread identifiers, corresponding to threads which are currently in a deadlocked situation, or null if there are no deadlocks.

Throws: SecurityException if a security manager exists and denies ManagementPermission("monitor").

See Also: findDeadlockedThreads

Returns all live thread identifiers at the time of initial execution. Some thread identifiers in the returned array may refer to terminated threads, if this occurs during the lifetime of this method.

Returns: an array of thread identifiers, corresponding to current live threads.

Throws: SecurityException if a security manager exists and denies ManagementPermission("monitor").

Returns the total number of nanoseconds of CPU time the current thread has used. This is equivalent to calling {@link #getThreadCpuTime()}(Thread.currentThread.getId()).

Note that the value is only nanosecond-precise, and not accurate; there is no guarantee that the difference between two values is really a nanosecond. Also, the value is prone to overflow if the offset exceeds 2^63. The use of this method depends on virtual machine support for measurement of the CPU time of the current thread, and on this functionality being enabled.

Returns: the total number of nanoseconds of CPU time the current thread has used, or -1 if CPU time monitoring is disabled.

Throws: UnsupportedOperationException if CPU time monitoring is not supported.

See Also: getCurrentThreadUserTime isCurrentThreadCpuTimeSupported isThreadCpuTimeEnabled ThreadMXBean

Returns the total number of nanoseconds of CPU time the current thread has executed in user mode. This is equivalent to calling {@link #getThreadUserTime()}(Thread.currentThread.getId()).

Note that the value is only nanosecond-precise, and not accurate; there is no guarantee that the difference between two values is really a nanosecond. Also, the value is prone to overflow if the offset exceeds 2^63. The use of this method depends on virtual machine support for measurement of the CPU time of the current thread, and on this functionality being enabled.

Returns: the total number of nanoseconds of CPU time the current thread has executed in user mode, or -1 if CPU time monitoring is disabled.

Throws: UnsupportedOperationException if CPU time monitoring is not supported.

See Also: getCurrentThreadCpuTime isCurrentThreadCpuTimeSupported isThreadCpuTimeEnabled ThreadMXBean

Returns the number of live daemon threads.

Returns: the number of live daemon threads.

Returns the peak number of live threads since the virtual machine was started or the count reset using {@link #resetPeakThreadCount()}.

Returns: the peak live thread count.

See Also: resetPeakThreadCount

Returns the number of live threads, including both daemon threads and non-daemon threads.

Returns: the current number of live threads.

Returns the total number of nanoseconds of CPU time the specified thread has used.

Note that the value is only nanosecond-precise, and not accurate; there is no guarantee that the difference between two values is really a nanosecond. Also, the value is prone to overflow if the offset exceeds 2^63. The use of this method depends on virtual machine support for measurement of the CPU time of the current thread, and on this functionality being enabled.

Parameters: id the thread identifier of the thread whose CPU time is being monitored.

Returns: the total number of nanoseconds of CPU time the specified thread has used, or -1 if CPU time monitoring is disabled.

Throws: IllegalArgumentException if id <= 0. UnsupportedOperationException if CPU time monitoring is not supported.

See Also: ThreadMXBean isThreadCpuTimeSupported isThreadCpuTimeEnabled ThreadMXBean

Returns information on the specified thread without any stack trace information. This is equivalent to {@link #getThreadInfo}(id, 0). If the identifier specifies a thread which is either non-existant or not alive, then the method returns null.

Parameters: id the identifier of the thread to return information on.

Returns: a {@link ThreadInfo} object pertaining to the specified thread, or null if the identifier specifies a thread that doesn't exist or is not alive.

Throws: IllegalArgumentException if id <= 0. SecurityException if a security manager exists and denies ManagementPermission("monitor").

Returns information on the specified threads without any stack trace information. This is equivalent to {@link #getThreadInfo}(ids, 0). If an identifier specifies a thread which is either non-existant or not alive, then the corresponding element in the returned array is null.

Parameters: ids an array of thread identifiers to return information on.

Returns: an array of {@link ThreadInfo} objects matching the specified threads. The corresponding element is null if the identifier specifies a thread that doesn't exist or is not alive.

Throws: IllegalArgumentException if an identifier in the array is <= 0. SecurityException if a security manager exists and denies ManagementPermission("monitor").

Returns information on the specified threads with full stack trace information and optional synchronization information. If lockedMonitors is false, or there are no locked monitors for a particular thread, then the corresponding {@link ThreadInfo} object will have an empty {@link MonitorInfo} array. Likewise, if lockedSynchronizers is false, or there are no locked ownable synchronizers for a particular thread, then the corresponding {@link ThreadInfo} object will have an empty {@link LockInfo} array. If both lockedMonitors and lockedSynchronizers are false, the return value is equivalent to that from {@link #getThreadInfo}(ids, Integer.MAX_VALUE). If an identifier specifies a thread which is either non-existant or not alive, then the corresponding element in the returned array is null.

Parameters: ids an array of thread identifiers to return information on. lockedMonitors true if information on locked monitors should be included. lockedSynchronizers true if information on locked ownable synchronizers should be included.

Returns: an array of {@link ThreadInfo} objects matching the specified threads. The corresponding element is null if the identifier specifies a thread that doesn't exist or is not alive.

Throws: IllegalArgumentException if an identifier in the array is <= 0. SecurityException if a security manager exists and denies ManagementPermission("monitor"). UnsupportedOperationException if lockedMonitors is true, but object monitor usage monitoring is not supported by the VM, or lockedSynchronizers is true, but ownable synchronizer usage monitoring is not supported by the VM.

Since: 1.6

See Also: isObjectMonitorUsageSupported isSynchronizerUsageSupported

Returns information on the specified thread with stack trace information to the supplied depth. If the identifier specifies a thread which is either non-existant or not alive, then the method returns null. A maximum depth of 0 corresponds to an empty stack trace (an empty array is returned by the appropriate {@link ThreadInfo} method). A maximum depth of Integer.MAX_VALUE returns the full stack trace.

Parameters: id the identifier of the thread to return information on. maxDepth the maximum depth of the stack trace. Values of 0 or Integer.MAX_VALUE correspond to an empty and full stack trace respectively.

Returns: a {@link ThreadInfo} object pertaining to the specified thread, or null if the identifier specifies a thread that doesn't exist or is not alive.

Throws: IllegalArgumentException if id <= 0. IllegalArgumentException if maxDepth < 0. SecurityException if a security manager exists and denies ManagementPermission("monitor").

Returns information on the specified threads with stack trace information to the supplied depth. If an identifier specifies a thread which is either non-existant or not alive, then the corresponding element in the returned array is null. A maximum depth of 0 corresponds to an empty stack trace (an empty array is returned by the appropriate {@link ThreadInfo} method). A maximum depth of Integer.MAX_VALUE returns the full stack trace.

Parameters: ids an array of thread identifiers to return information on. maxDepth the maximum depth of the stack trace. Values of 0 or Integer.MAX_VALUE correspond to an empty and full stack trace respectively.

Returns: an array of {@link ThreadInfo} objects matching the specified threads. The corresponding element is null if the identifier specifies a thread that doesn't exist or is not alive.

Throws: IllegalArgumentException if an identifier in the array is <= 0. IllegalArgumentException if maxDepth < 0. SecurityException if a security manager exists and denies ManagementPermission("monitor").

Returns the total number of nanoseconds of CPU time the specified thread has executed in user mode.

Note that the value is only nanosecond-precise, and not accurate; there is no guarantee that the difference between two values is really a nanosecond. Also, the value is prone to overflow if the offset exceeds 2^63. The use of this method depends on virtual machine support for measurement of the CPU time of the current thread, and on this functionality being enabled.

Parameters: id the thread identifier of the thread whose CPU time is being monitored.

Returns: the total number of nanoseconds of CPU time the specified thread has executed in user mode, or -1 if CPU time monitoring is disabled.

Throws: IllegalArgumentException if id <= 0. UnsupportedOperationException if CPU time monitoring is not supported.

See Also: ThreadMXBean isThreadCpuTimeSupported isThreadCpuTimeEnabled ThreadMXBean

Returns the total number of threads that have been created and started during the lifetime of the virtual machine.

Returns: the total number of started threads.

Returns true if the virtual machine supports the monitoring of the CPU time used by the current thread. This is implied by {@link isThreadCpuTimeSupported()} returning true.

Returns: true if monitoring of the CPU time used by the current thread is supported by the virtual machine.

See Also: isThreadCpuTimeEnabled isThreadCpuTimeSupported ThreadMXBean

Returns true if the virtual machine supports the monitoring of object monitor usage.

Returns: true if the monitoring of object monitor usage is supported by the virtual machine.

Since: 1.6

Returns true if the virtual machine supports the monitoring of ownable synchronizer usage.

Returns: true if the monitoring of ownable synchronizer usage is supported by the virtual machine.

Since: 1.6

Returns true if thread contention monitoring is currently enabled.

Returns: true if thread contention monitoring is enabled.

Throws: UnsupportedOperationException if the virtual machine does not support contention monitoring.

See Also: isThreadContentionMonitoringSupported ThreadMXBean

Returns true if thread contention monitoring is supported by the virtual machine.

Returns: true if thread contention monitoring is supported by the virtual machine.

See Also: isThreadContentionMonitoringEnabled ThreadMXBean

Returns true if monitoring of the CPU time used by a thread is currently enabled.

Returns: true if thread CPU time monitoring is enabled.

Throws: UnsupportedOperationException if the virtual machine does not support CPU time monitoring.

See Also: isCurrentThreadCpuTimeSupported isThreadCpuTimeSupported ThreadMXBean

Returns true if the virtual machine supports the monitoring of the CPU time used by all threads. This implies that {@link isCurrentThreadCpuTimeSupported()} returns true.

Returns: true if monitoring of the CPU time used by the current thread is supported by the virtual machine.

See Also: isCurrentThreadCpuTimeSupported isThreadCpuTimeEnabled ThreadMXBean

Resets the peak live thread count to the current number of live threads, as returned by {@link #getThreadCount()}.

Throws: SecurityException if a security manager exists and denies ManagementPermission("control").

See Also: getPeakThreadCount getThreadCount

Toggles the monitoring of thread contention. Thread contention monitoring is disabled by default. Each time contention monitoring is re-enabled, the times it maintains are reset.

Parameters: enable true if monitoring should be enabled, false if it should be disabled.

Throws: UnsupportedOperationException if the virtual machine does not support contention monitoring. SecurityException if a security manager exists and denies ManagementPermission("control").

See Also: isThreadContentionMonitoringEnabled isThreadContentionMonitoringSupported

Toggles the monitoring of CPU time used by threads. The initial setting is dependent on the underlying virtual machine. On enabling CPU time monitoring, the virtual machine may take any value up to and including the current time as the start time for monitoring.

Parameters: enable true if monitoring should be enabled, false if it should be disabled.

Throws: UnsupportedOperationException if the virtual machine does not support CPU time monitoring. SecurityException if a security manager exists and denies ManagementPermission("control").

See Also: isCurrentThreadCpuTimeSupported isThreadCpuTimeEnabled isThreadCpuTimeSupported