Module java.management

Package java.lang.management

Class ThreadInfo

java.lang.Object

java.lang.management.ThreadInfo

public class ThreadInfo
extends Object

Thread information. ThreadInfo contains the information about a thread including:

General thread information

• Thread ID.
• Name of the thread.
• Whether a thread is a daemon thread

Execution information

• Thread state.
• The object upon which the thread is blocked due to:
  • waiting to enter a synchronization block/method, or
  • waiting to be notified in a Object.wait method, or
  • parking due to a LockSupport.park call.
• The ID of the thread that owns the object that the thread is blocked.
• Stack trace of the thread.
• List of object monitors locked by the thread.
• List of ownable synchronizers locked by the thread.
• Thread priority

Synchronization Statistics

• The number of times that the thread has blocked for synchronization or waited for notification.
• The accumulated elapsed time that the thread has blocked for synchronization or waited for notification since thread contention monitoring was enabled. Some Java virtual machine implementation may not support this. The ThreadMXBean.isThreadContentionMonitoringSupported() method can be used to determine if a Java virtual machine supports this.

This thread information class is designed for use in monitoring of the system, not for synchronization control.

MXBean Mapping

ThreadInfo is mapped to a CompositeData with attributes as specified in the from method.

Since:

1.5

See Also:

• ThreadMXBean.getThreadInfo(long)
• ThreadMXBean.dumpAllThreads(boolean, boolean)

Method Summary

Modifier and Type	Method	Description
static ThreadInfo	from(CompositeData cd)	Returns a ThreadInfo object represented by the given CompositeData.
long	getBlockedCount()	Returns the total number of times that the thread associated with this ThreadInfo blocked to enter or reenter a monitor.
long	getBlockedTime()	Returns the approximate accumulated elapsed time (in milliseconds) that the thread associated with this ThreadInfo has blocked to enter or reenter a monitor since thread contention monitoring is enabled.
MonitorInfo[]	getLockedMonitors()	Returns an array of MonitorInfo objects, each of which represents an object monitor currently locked by the thread associated with this ThreadInfo.
LockInfo[]	getLockedSynchronizers()	Returns an array of LockInfo objects, each of which represents an ownable synchronizer currently locked by the thread associated with this ThreadInfo.
LockInfo	getLockInfo()	Returns the LockInfo of an object for which the thread associated with this ThreadInfo is blocked waiting.
String	getLockName()	Returns the string representation of an object for which the thread associated with this ThreadInfo is blocked waiting.
long	getLockOwnerId()	Returns the ID of the thread which owns the object for which the thread associated with this ThreadInfo is blocked waiting.
String	getLockOwnerName()	Returns the name of the thread which owns the object for which the thread associated with this ThreadInfo is blocked waiting.
int	getPriority()	Returns the thread priority of the thread associated with this ThreadInfo.
StackTraceElement[]	getStackTrace()	Returns the stack trace of the thread associated with this ThreadInfo.
long	getThreadId()	Returns the ID of the thread associated with this ThreadInfo.
String	getThreadName()	Returns the name of the thread associated with this ThreadInfo.
Thread.State	getThreadState()	Returns the state of the thread associated with this ThreadInfo.
long	getWaitedCount()	Returns the total number of times that the thread associated with this ThreadInfo waited for notification.
long	getWaitedTime()	Returns the approximate accumulated elapsed time (in milliseconds) that the thread associated with this ThreadInfo has waited for notification since thread contention monitoring is enabled.
boolean	isDaemon()	Tests if the thread associated with this ThreadInfo is a daemon thread.
boolean	isInNative()	Tests if the thread associated with this ThreadInfo is executing native code.
boolean	isSuspended()	Tests if the thread associated with this ThreadInfo is suspended.
String	toString()	Returns a string representation of this thread info.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Details

getThreadId

public long getThreadId()

Returns the ID of the thread associated with this ThreadInfo.

Returns:

the ID of the associated thread.

getThreadName

public String getThreadName()

Returns the name of the thread associated with this ThreadInfo.

Returns:

the name of the associated thread.

getThreadState

public Thread.State getThreadState()

Returns the state of the thread associated with this ThreadInfo.

Returns:

Thread.State of the associated thread.

getBlockedTime

public long getBlockedTime()

Returns the approximate accumulated elapsed time (in milliseconds) that the thread associated with this ThreadInfo has blocked to enter or reenter a monitor since thread contention monitoring is enabled. I.e. the total accumulated time the thread has been in the BLOCKED state since thread contention monitoring was last enabled. This method returns -1 if thread contention monitoring is disabled.

The Java virtual machine may measure the time with a high resolution timer. This statistic is reset when the thread contention monitoring is re-enabled.

Returns:

the approximate accumulated elapsed time in milliseconds that a thread entered the BLOCKED state; -1 if thread contention monitoring is disabled.

Throws:

UnsupportedOperationException - if the Java virtual machine does not support this operation.

See Also:

• ThreadMXBean.isThreadContentionMonitoringSupported()
• ThreadMXBean.setThreadContentionMonitoringEnabled(boolean)

getBlockedCount

public long getBlockedCount()

Returns the total number of times that the thread associated with this ThreadInfo blocked to enter or reenter a monitor. I.e. the number of times a thread has been in the BLOCKED state.

Returns:

the total number of times that the thread entered the BLOCKED state.

getWaitedTime

public long getWaitedTime()

Returns the approximate accumulated elapsed time (in milliseconds) that the thread associated with this ThreadInfo has waited for notification since thread contention monitoring is enabled. I.e. the total accumulated time the thread has been in the WAITING or TIMED_WAITING state since thread contention monitoring is enabled. This method returns -1 if thread contention monitoring is disabled.

The Java virtual machine may measure the time with a high resolution timer. This statistic is reset when the thread contention monitoring is re-enabled.

Returns:

the approximate accumulated elapsed time in milliseconds that a thread has been in the WAITING or TIMED_WAITING state; -1 if thread contention monitoring is disabled.

Throws:

UnsupportedOperationException - if the Java virtual machine does not support this operation.

See Also:

• ThreadMXBean.isThreadContentionMonitoringSupported()
• ThreadMXBean.setThreadContentionMonitoringEnabled(boolean)

getWaitedCount

public long getWaitedCount()

Returns the total number of times that the thread associated with this ThreadInfo waited for notification. I.e. the number of times that a thread has been in the WAITING or TIMED_WAITING state.

Returns:

the total number of times that the thread was in the WAITING or TIMED_WAITING state.

getLockInfo

public LockInfo getLockInfo()

Returns the LockInfo of an object for which the thread associated with this ThreadInfo is blocked waiting. A thread can be blocked waiting for one of the following:

• an object monitor to be acquired for entering or reentering a synchronization block/method.
  The thread is in the BLOCKED state waiting to enter the synchronized statement or method.
• an object monitor to be notified by another thread.
  The thread is in the WAITING or TIMED_WAITING state due to a call to the Object.wait method.
• a synchronization object responsible for the thread parking.
  The thread is in the WAITING or TIMED_WAITING state due to a call to the LockSupport.park method. The synchronization object is the object returned from LockSupport.getBlocker method. Typically it is an ownable synchronizer or a Condition.

This method returns null if the thread is not in any of the above conditions.

Returns:

LockInfo of an object for which the thread is blocked waiting if any; null otherwise.

Since:

1.6

getLockName

public String getLockName()

Returns the string representation of an object for which the thread associated with this ThreadInfo is blocked waiting. This method is equivalent to calling:

 getLockInfo().toString()
 

This method will return null if this thread is not blocked waiting for any object or if the object is not owned by any thread.

Returns:

the string representation of the object on which the thread is blocked if any; null otherwise.

See Also:

• getLockInfo()

getLockOwnerId

public long getLockOwnerId()

Returns the ID of the thread which owns the object for which the thread associated with this ThreadInfo is blocked waiting. This method will return -1 if this thread is not blocked waiting for any object or if the object is not owned by any thread.

Returns:

the thread ID of the owner thread of the object this thread is blocked on; -1 if this thread is not blocked or if the object is not owned by any thread.

See Also:

• getLockInfo()

getLockOwnerName

public String getLockOwnerName()

Returns the name of the thread which owns the object for which the thread associated with this ThreadInfo is blocked waiting. This method will return null if this thread is not blocked waiting for any object or if the object is not owned by any thread.

Returns:

the name of the thread that owns the object this thread is blocked on; null if this thread is not blocked or if the object is not owned by any thread.

See Also:

• getLockInfo()

getStackTrace

public StackTraceElement[] getStackTrace()

Returns the stack trace of the thread associated with this ThreadInfo. If no stack trace was requested for this thread info, this method will return a zero-length array. If the returned array is of non-zero length then the first element of the array represents the top of the stack, which is the most recent method invocation in the sequence. The last element of the array represents the bottom of the stack, which is the least recent method invocation in the sequence.

Some Java virtual machines may, under some circumstances, omit one or more stack frames from the stack trace. In the extreme case, a virtual machine that has no stack trace information concerning the thread associated with this ThreadInfo is permitted to return a zero-length array from this method.

Returns:

an array of StackTraceElement objects of the thread.

isSuspended

public boolean isSuspended()

Tests if the thread associated with this ThreadInfo is suspended. This method returns true if Thread.suspend() has been called.

Returns:

true if the thread is suspended; false otherwise.

isInNative

public boolean isInNative()

Tests if the thread associated with this ThreadInfo is executing native code.

A thread is considered to be executing native code when it is executing a native method, executing native code invoked using a method handle^RESTRICTED obtained from the native linker, or is attached to the VM with the Java Native Interface with no Java frames on its stack.

Native code does not include Java virtual machine support code, compiled code generated by the Java virtual machine, or special cases such as a thread blocked on a JVM TI raw monitor.

Returns:

true if the thread is executing native code; false otherwise.

isDaemon

public boolean isDaemon()

Tests if the thread associated with this ThreadInfo is a daemon thread.

Returns:

true if the thread is a daemon thread, false otherwise.

Since:

9

See Also:

• Thread.isDaemon()

getPriority

public int getPriority()

Returns the thread priority of the thread associated with this ThreadInfo.

Returns:

The priority of the thread associated with this ThreadInfo.

Since:

9

toString

public String toString()

Returns a string representation of this thread info. The format of this string depends on the implementation. The returned string will typically include the thread name, the thread ID, its state, and a stack trace if any.

Overrides:

toString in class Object

Returns:

a string representation of this thread info.

from

public static ThreadInfo from(CompositeData cd)

Returns a ThreadInfo object represented by the given CompositeData. A CompositeData representing a ThreadInfo of version N must contain all of the attributes defined in version ≤ N unless specified otherwise. The same rule applies the composite type of the given CompositeData and transitively to attributes whose type or component type is CompositeType.

A CompositeData representing ThreadInfo of version N contains "stackTrace" attribute and "lockedMonitors" attribute representing an array of StackTraceElement and an array of MonitorInfo respectively and their types are of version N. The "lockedStackFrame" attribute in MonitorInfo's composite type must represent StackTraceElement of the same version N. Otherwise, this method will throw IllegalArgumentException.

The attributes and their types for ThreadInfo's composite data

Attribute Name	Type	Since
threadId	java.lang.Long	5
threadName	java.lang.String	5
threadState	java.lang.String	5
suspended	java.lang.Boolean	5
inNative	java.lang.Boolean	5
blockedCount	java.lang.Long	5
blockedTime	java.lang.Long	5
waitedCount	java.lang.Long	5
waitedTime	java.lang.Long	5
lockName	java.lang.String	5
lockOwnerId	java.lang.Long	5
lockOwnerName	java.lang.String	5
stackTrace	javax.management.openmbean.CompositeData[], each element is a CompositeData representing StackTraceElement as specified below.	5
lockInfo	javax.management.openmbean.CompositeData - the mapped type for LockInfo as specified in the LockInfo.from(javax.management.openmbean.CompositeData) method. If the given CompositeData does not contain this attribute, the LockInfo object will be constructed from the value of the lockName attribute.	6
lockedMonitors	javax.management.openmbean.CompositeData[] whose element type is the mapped type for MonitorInfo as specified in the MonitorInfo.from method. If the given CompositeData does not contain this attribute, this attribute will be set to an empty array.	6
lockedSynchronizers	javax.management.openmbean.CompositeData[] whose element type is the mapped type for LockInfo as specified in the LockInfo.from(javax.management.openmbean.CompositeData) method. If the given CompositeData does not contain this attribute, this attribute will be set to an empty array.	6
daemon	java.lang.Boolean If the given CompositeData does not contain this attribute, this attribute will be set to false.	9
priority	java.lang.Integer If the given CompositeData does not contain this attribute, This attribute will be set to Thread.NORM_PRIORITY.	9

A CompositeData representing StackTraceElement of version N must contain all of the attributes defined in version ≤ N unless specified otherwise.

The attributes and their types for StackTraceElement's composite data

Attribute Name	Type	Since
classLoaderName	java.lang.String	9
moduleName	java.lang.String	9
moduleVersion	java.lang.String	9
className	java.lang.String	5
methodName	java.lang.String	5
fileName	java.lang.String	5
lineNumber	java.lang.Integer	5
nativeMethod	java.lang.Boolean	5

Parameters:

cd - CompositeData representing a ThreadInfo

Returns:

a ThreadInfo object represented by cd if cd is not null; null otherwise.

Throws:

IllegalArgumentException - if the given cd and its composite type does not contain all of the attributes defined for a ThreadInfo of a specific runtime version.

getLockedMonitors

public MonitorInfo[] getLockedMonitors()

Returns an array of MonitorInfo objects, each of which represents an object monitor currently locked by the thread associated with this ThreadInfo. If no locked monitor was requested for this thread info or no monitor is locked by the thread, this method will return a zero-length array.

Returns:

an array of MonitorInfo objects representing the object monitors locked by the thread.

Since:

1.6

getLockedSynchronizers

public LockInfo[] getLockedSynchronizers()

Returns an array of LockInfo objects, each of which represents an ownable synchronizer currently locked by the thread associated with this ThreadInfo. If no locked synchronizer was requested for this thread info or no synchronizer is locked by the thread, this method will return a zero-length array.

Returns:

an array of LockInfo objects representing the ownable synchronizers locked by the thread.

Since:

1.6