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/OpenJDK 21

Interface ThreadMXBean

All Superinterfaces:
PlatformManagedObject, ThreadMXBean 
public interface ThreadMXBean extends ThreadMXBean
Platform-specific management interface for the thread system of the Java virtual machine.

This platform extension is only available to a thread implementation that supports this extension.

Since:
6u25

Method Summary

Modifier and Type Method Description
default long getCurrentThreadAllocatedBytes()
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for the current thread.
long getThreadAllocatedBytes(long id)
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for the thread with the specified ID.
long[] getThreadAllocatedBytes(long[] ids)
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for each thread whose ID is in the input array ids.
long[] getThreadCpuTime(long[] ids)
Returns the total CPU time for each thread whose ID is in the input array ids in nanoseconds.
long[] getThreadUserTime(long[] ids)
Returns the CPU time that each thread whose ID is in the input array ids has executed in user mode in nanoseconds.
default long getTotalThreadAllocatedBytes()
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory by all threads since the Java virtual machine started.
boolean isThreadAllocatedMemoryEnabled()
Tests if thread memory allocation measurement is enabled.
boolean isThreadAllocatedMemorySupported()
Tests if the Java virtual machine implementation supports thread memory allocation measurement.
void setThreadAllocatedMemoryEnabled(boolean enable)
Enables or disables thread memory allocation measurement.

Methods declared in interface java.lang.management.PlatformManagedObject

getObjectName

Methods declared in interface java.lang.management.ThreadMXBean

dumpAllThreads, dumpAllThreads, findDeadlockedThreads, findMonitorDeadlockedThreads, getAllThreadIds, getCurrentThreadCpuTime, getCurrentThreadUserTime, getDaemonThreadCount, getPeakThreadCount, getThreadCount, getThreadCpuTime, getThreadInfo, getThreadInfo, getThreadInfo, getThreadInfo, getThreadInfo, getThreadInfo, getThreadUserTime, getTotalStartedThreadCount, isCurrentThreadCpuTimeSupported, isObjectMonitorUsageSupported, isSynchronizerUsageSupported, isThreadContentionMonitoringEnabled, isThreadContentionMonitoringSupported, isThreadCpuTimeEnabled, isThreadCpuTimeSupported, resetPeakThreadCount, setThreadContentionMonitoringEnabled, setThreadCpuTimeEnabled

Method Details

getThreadCpuTime

long[] getThreadCpuTime(long[] ids)
Returns the total CPU time for each thread whose ID is in the input array ids in nanoseconds. The returned values are of nanoseconds precision but not necessarily nanoseconds accuracy.

This method is equivalent to calling the ThreadMXBean.getThreadCpuTime(long) method for each thread ID in the input array ids and setting the returned value in the corresponding element of the returned array.

Parameters:
ids - an array of thread IDs.
Returns:
an array of long values, each of which is the amount of CPU time the thread whose ID is in the corresponding element of the input array of IDs has used, if the thread of a specified ID is a platform thread, the thread is alive, and CPU time measurement is enabled; -1 otherwise.
Throws:
NullPointerException - if ids is null
IllegalArgumentException - if any element in the input array ids is <= 0.
UnsupportedOperationException - if the Java virtual machine implementation does not support CPU time measurement.
See Also:

getThreadUserTime

long[] getThreadUserTime(long[] ids)
Returns the CPU time that each thread whose ID is in the input array ids has executed in user mode in nanoseconds. The returned values are of nanoseconds precision but not necessarily nanoseconds accuracy.

This method is equivalent to calling the ThreadMXBean.getThreadUserTime(long) method for each thread ID in the input array ids and setting the returned value in the corresponding element of the returned array.

Parameters:
ids - an array of thread IDs.
Returns:
an array of long values, each of which is the amount of user mode CPU time the thread whose ID is in the corresponding element of the input array of IDs has used, if the thread of a specified ID is a platform thread, the thread is alive, and CPU time measurement is enabled; -1 otherwise.
Throws:
NullPointerException - if ids is null
IllegalArgumentException - if any element in the input array ids is <= 0.
UnsupportedOperationException - if the Java virtual machine implementation does not support CPU time measurement.
See Also:

getTotalThreadAllocatedBytes

default long getTotalThreadAllocatedBytes()
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory by all threads since the Java virtual machine started. The returned value is an approximation because some Java virtual machine implementations may use object allocation mechanisms that result in a delay between the time an object is allocated and the time its size is recorded.
Implementation Requirements:
The default implementation throws UnsupportedOperationException if the Java virtual machine implementation does not support thread memory allocation measurement, and otherwise acts as though thread memory allocation measurement is disabled.
Returns:
an approximation of the total memory allocated, in bytes, in heap memory since the Java virtual machine was started, if thread memory allocation measurement is enabled; -1 otherwise.
Throws:
UnsupportedOperationException - if the Java virtual machine implementation does not support thread memory allocation measurement.
Since:
21
See Also:

getCurrentThreadAllocatedBytes

default long getCurrentThreadAllocatedBytes()
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for the current thread. The returned value is an approximation because some Java virtual machine implementations may use object allocation mechanisms that result in a delay between the time an object is allocated and the time its size is recorded.

This is a convenience method for local management use and is equivalent to calling: 

   getThreadAllocatedBytes(Thread.currentThread().threadId());
Returns:
an approximation of the total memory allocated, in bytes, in heap memory for the current thread if thread memory allocation measurement is enabled; -1 otherwise.
Throws:
UnsupportedOperationException - if the Java virtual machine implementation does not support thread memory allocation measurement.
Since:
14
See Also:

getThreadAllocatedBytes

long getThreadAllocatedBytes(long id)
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for the thread with the specified ID. The returned value is an approximation because some Java virtual machine implementations may use object allocation mechanisms that result in a delay between the time an object is allocated and the time its size is recorded.

If the thread with the specified ID is a virtual thread, is not alive, or does not exist, this method returns -1. If thread memory allocation measurement is disabled, this method returns -1. A thread is alive if it has been started and has not yet terminated.

If thread memory allocation measurement is enabled after the thread has started, the Java virtual machine implementation may choose any time up to and including the time that the capability is enabled as the point where thread memory allocation measurement starts.

Parameters:
id - the thread ID of a thread
Returns:
an approximation of the total memory allocated, in bytes, in heap memory for the thread with the specified ID if the thread with the specified ID is a platform thread, the thread is alive, and thread memory allocation measurement is enabled; -1 otherwise.
Throws:
IllegalArgumentException - if id <= 0.
UnsupportedOperationException - if the Java virtual machine implementation does not support thread memory allocation measurement.
See Also:

getThreadAllocatedBytes

long[] getThreadAllocatedBytes(long[] ids)
Returns an approximation of the total amount of memory, in bytes, allocated in heap memory for each thread whose ID is in the input array ids. The returned values are approximations because some Java virtual machine implementations may use object allocation mechanisms that result in a delay between the time an object is allocated and the time its size is recorded.

This method is equivalent to calling the getThreadAllocatedBytes(long) method for each thread ID in the input array ids and setting the returned value in the corresponding element of the returned array.

Parameters:
ids - an array of thread IDs.
Returns:
an array of long values, each of which is an approximation of the total memory allocated, in bytes, in heap memory for the thread whose ID is in the corresponding element of the input array of IDs.
Throws:
NullPointerException - if ids is null
IllegalArgumentException - if any element in the input array ids is <= 0.
UnsupportedOperationException - if the Java virtual machine implementation does not support thread memory allocation measurement.
See Also:

isThreadAllocatedMemorySupported

boolean isThreadAllocatedMemorySupported()
Tests if the Java virtual machine implementation supports thread memory allocation measurement.
Returns:
true if the Java virtual machine implementation supports thread memory allocation measurement; false otherwise.

isThreadAllocatedMemoryEnabled

boolean isThreadAllocatedMemoryEnabled()
Tests if thread memory allocation measurement is enabled.
Returns:
true if thread memory allocation measurement is enabled; false otherwise.
Throws:
UnsupportedOperationException - if the Java virtual machine does not support thread memory allocation measurement.
See Also:

setThreadAllocatedMemoryEnabled

void setThreadAllocatedMemoryEnabled(boolean enable)
Enables or disables thread memory allocation measurement. The default is platform dependent.
Parameters:
enable - true to enable; false to disable.
Throws:
UnsupportedOperationException - if the Java virtual machine does not support thread memory allocation measurement.
SecurityException - if a security manager exists and the caller does not have ManagementPermission("control").
See Also:

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.management/com/sun/management/ThreadMXBean.html