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.

  #### 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.

  #### 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

    Methods
    Modifier and Type | Method and 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.
    `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` | `isInNative()` Tests if the thread associated with this `ThreadInfo` is executing native code via the Java Native Interface (JNI).
    `boolean` | `isSuspended()` Tests if the thread associated with this `ThreadInfo` is suspended.
    `String` | `toString()` Returns a string representation of this thread info.

    - ### Methods inherited from class java.lang.Object

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

- - ### Method Detail

    - #### 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 reenabled.

      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 reenabled.

      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 via the Java Native Interface (JNI). The JNI native code does not include the virtual machine support code or the compiled native code generated by the virtual machine.
      Returns:
        `true` if the thread is executing native code; `false` otherwise.

    - #### 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`. The given `CompositeData` must contain the following attributes unless otherwise specified below:

      > Attribute Name | Type
      > --- | ---
      > threadId | `java.lang.Long`
      > threadName | `java.lang.String`
      > threadState | `java.lang.String`
      > suspended | `java.lang.Boolean`
      > inNative | `java.lang.Boolean`
      > blockedCount | `java.lang.Long`
      > blockedTime | `java.lang.Long`
      > waitedCount | `java.lang.Long`
      > waitedTime | `java.lang.Long`
      > lockInfo | `javax.management.openmbean.CompositeData` - the mapped type for `LockInfo` as specified in the type mapping rules of MXBeans. If `cd` does not contain this attribute, the `LockInfo` object will be constructed from the value of the `lockName` attribute.
      > lockName | `java.lang.String`
      > lockOwnerId | `java.lang.Long`
      > lockOwnerName | `java.lang.String`
      > > stackTrace | `javax.management.openmbean.CompositeData[]` Each element is a `CompositeData` representing StackTraceElement containing the following attributes:
      > > Attribute Name | Type
      > > --- | ---
      > > className | `java.lang.String`
      > > methodName | `java.lang.String`
      > > fileName | `java.lang.String`
      > > lineNumber | `java.lang.Integer`
      > > nativeMethod | `java.lang.Boolean`
      > lockedMonitors | `javax.management.openmbean.CompositeData[]` whose element type is the mapped type for `MonitorInfo` as specified in the `Monitor.from` method. If `cd` does not contain this attribute, this attribute will be set to an empty array.
      > lockedSynchronizers | `javax.management.openmbean.CompositeData[]` whose element type is the mapped type for `LockInfo` as specified in the type mapping rules of MXBeans. If `cd` does not contain this attribute, this attribute will be set to an empty array.

      Parameters:
        `cd` - `CompositeData` representing a `ThreadInfo`
      Returns:
        a `ThreadInfo` object represented by `cd` if `cd` is not `null`; `null` otherwise.
      Throws:
        `IllegalArgumentException` - if `cd` does not represent a `ThreadInfo` with the attributes described above.

    - #### 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

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