# Class ThreadUtils

java.lang.Object
org.apache.commons.lang3.ThreadUtils

public class ThreadUtils extends Object
Helpers for `Thread` and `ThreadGroup`.

#ThreadSafe#

Since:
  3.5
See Also:
  - `Thread`
  - `ThreadGroup`

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `ThreadUtils.NamePredicate`
  Deprecated.
  Use a `Predicate`.
  `static interface`
  `ThreadUtils.ThreadGroupPredicate`
  Deprecated.
  Use a `Predicate`.
  `static class`
  `ThreadUtils.ThreadIdPredicate`
  Deprecated.
  Use a `Predicate`.
  `static interface`
  `ThreadUtils.ThreadPredicate`
  Deprecated.
  Use a `Predicate`.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final org.apache.commons.lang3.ThreadUtils.AlwaysTruePredicate`
  `ALWAYS_TRUE_PREDICATE`
  Deprecated.
  Use a `Predicate`.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `ThreadUtils()`
  Deprecated.
  TODO Make private in 4.0.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static Thread`
  `findThreadById(long threadId)`
  Finds the active thread with the specified id.
  `static Thread`
  `findThreadById(long threadId, String threadGroupName)`
  Finds the active thread with the specified id if it belongs to a thread group with the specified group name.
  `static Thread`
  `findThreadById(long threadId, ThreadGroup threadGroup)`
  Finds the active thread with the specified id if it belongs to the specified thread group.
  `static Collection<ThreadGroup>`
  `findThreadGroups(ThreadGroup threadGroup, boolean recurse, Predicate<ThreadGroup> predicate)`
  Finds all active thread groups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups).
  `static Collection<ThreadGroup>`
  `findThreadGroups(ThreadGroup threadGroup, boolean recurse, ThreadUtils.ThreadGroupPredicate predicate)`
  Deprecated.
  Use `findThreadGroups(ThreadGroup, boolean, Predicate)`.
  `static Collection<ThreadGroup>`
  `findThreadGroups(Predicate<ThreadGroup> predicate)`
  Finds all active thread groups which match the given predicate.
  `static Collection<ThreadGroup>`
  `findThreadGroups(ThreadUtils.ThreadGroupPredicate predicate)`
  Deprecated.
  Use `findThreadGroups(Predicate)`.
  `static Collection<ThreadGroup>`
  `findThreadGroupsByName(String threadGroupName)`
  Finds active thread groups with the specified group name.
  `static Collection<Thread>`
  `findThreads(ThreadGroup threadGroup, boolean recurse, Predicate<Thread> predicate)`
  Finds all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups).
  `static Collection<Thread>`
  `findThreads(ThreadGroup threadGroup, boolean recurse, ThreadUtils.ThreadPredicate predicate)`
  Deprecated.
  Use `findThreads(ThreadGroup, boolean, Predicate)`.
  `static Collection<Thread>`
  `findThreads(Predicate<Thread> predicate)`
  Finds all active threads which match the given predicate.
  `static Collection<Thread>`
  `findThreads(ThreadUtils.ThreadPredicate predicate)`
  Deprecated.
  Use `findThreads(Predicate)`.
  `static Collection<Thread>`
  `findThreadsByName(String threadName)`
  Finds active threads with the specified name.
  `static Collection<Thread>`
  `findThreadsByName(String threadName, String threadGroupName)`
  Finds active threads with the specified name if they belong to a thread group with the specified group name.
  `static Collection<Thread>`
  `findThreadsByName(String threadName, ThreadGroup threadGroup)`
  Finds active threads with the specified name if they belong to a specified thread group.
  `static Collection<ThreadGroup>`
  `getAllThreadGroups()`
  Gets all active thread groups excluding the system thread group (A thread group is active if it has been not destroyed).
  `static Collection<Thread>`
  `getAllThreads()`
  Gets all active threads (A thread is active if it has been started and has not yet died).
  `static ThreadGroup`
  `getSystemThreadGroup()`
  Gets the system thread group (sometimes also referred as "root thread group").
  `static void`
  `join(Thread thread, Duration duration)`
  Waits for the given thread to die for the given duration.
  `static void`
  `sleep(Duration duration)`
  Sleeps the current thread for the given duration.
  `static void`
  `sleepQuietly(Duration duration)`
  Sleeps for the given duration while ignoring `InterruptedException`.

  ### Methods inherited from class Object

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

- ## Field Details

  - ### ALWAYS_TRUE_PREDICATE

    @Deprecated public static final org.apache.commons.lang3.ThreadUtils.AlwaysTruePredicate ALWAYS_TRUE_PREDICATE
    Deprecated.
    Use a `Predicate`.
    Predicate which always returns true.

- ## Constructor Details

  - ### ThreadUtils

    @Deprecated public ThreadUtils()
    Deprecated.
    TODO Make private in 4.0.
    ThreadUtils instances should NOT be constructed in standard programming. Instead, the class should be used as `ThreadUtils.getAllThreads()`

    This constructor is public to permit tools that require a JavaBean instance to operate.

- ## Method Details

  - ### findThreadById

    public static Thread findThreadById(long threadId)
    Finds the active thread with the specified id.
    Parameters:
      `threadId` - The thread id.
    Returns:
      The thread with the specified id or `null` if no such thread exists.
    Throws:
      `IllegalArgumentException` - if the specified id is zero or negative.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadById

    public static Thread findThreadById(long threadId, String threadGroupName)
    Finds the active thread with the specified id if it belongs to a thread group with the specified group name.
    Parameters:
      `threadId` - The thread id.
      `threadGroupName` - The thread group name.
    Returns:
      The threads which belongs to a thread group with the specified group name and the thread's id match the specified id. `null` is returned if no such thread exists.
    Throws:
      `NullPointerException` - if the group name is null.
      `IllegalArgumentException` - if the specified id is zero or negative.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadById

    public static Thread findThreadById(long threadId, ThreadGroup threadGroup)
    Finds the active thread with the specified id if it belongs to the specified thread group.
    Parameters:
      `threadId` - The thread id.
      `threadGroup` - The thread group.
    Returns:
      The thread which belongs to a specified thread group and the thread's id match the specified id. `null` is returned if no such thread exists.
    Throws:
      `NullPointerException` - if `threadGroup == null`.
      `IllegalArgumentException` - if the specified id is zero or negative.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadGroups

    public static Collection<ThreadGroup> findThreadGroups(Predicate<ThreadGroup> predicate)
    Finds all active thread groups which match the given predicate.
    Parameters:
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active thread groups matching the given predicate.
    Throws:
      `NullPointerException` - if the predicate is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.
    Since:
      3.13.0

  - ### findThreadGroups

    public static Collection<ThreadGroup> findThreadGroups(ThreadGroup threadGroup, boolean recurse, Predicate<ThreadGroup> predicate)
    Finds all active thread groups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups).
    Parameters:
      `threadGroup` - the thread group.
      `recurse` - if `true` then evaluate the predicate recursively on all thread groups in all subgroups of the given group.
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active thread groups which match the given predicate and which is a subgroup of the given thread group.
    Throws:
      `NullPointerException` - if the given group or predicate is null.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.
    Since:
      3.13.0

  - ### findThreadGroups

    @Deprecated public static Collection<ThreadGroup> findThreadGroups(ThreadGroup threadGroup, boolean recurse, ThreadUtils.ThreadGroupPredicate predicate)
    Deprecated.
    Use `findThreadGroups(ThreadGroup, boolean, Predicate)`.
    Finds all active thread groups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups).
    Parameters:
      `threadGroup` - the thread group.
      `recurse` - if `true` then evaluate the predicate recursively on all thread groups in all subgroups of the given group.
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active thread groups which match the given predicate and which is a subgroup of the given thread group.
    Throws:
      `NullPointerException` - if the given group or predicate is null.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadGroups

    @Deprecated public static Collection<ThreadGroup> findThreadGroups(ThreadUtils.ThreadGroupPredicate predicate)
    Deprecated.
    Use `findThreadGroups(Predicate)`.
    Finds all active thread groups which match the given predicate.
    Parameters:
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active thread groups matching the given predicate.
    Throws:
      `NullPointerException` - if the predicate is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadGroupsByName

    public static Collection<ThreadGroup> findThreadGroupsByName(String threadGroupName)
    Finds active thread groups with the specified group name.
    Parameters:
      `threadGroupName` - The thread group name.
    Returns:
      the thread groups with the specified group name or an empty collection if no such thread group exists. The collection returned is always unmodifiable.
    Throws:
      `NullPointerException` - if group name is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreads

    public static Collection<Thread> findThreads(Predicate<Thread> predicate)
    Finds all active threads which match the given predicate.
    Parameters:
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active threads matching the given predicate.
    Throws:
      `NullPointerException` - if the predicate is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.
    Since:
      3.13.0

  - ### findThreads

    public static Collection<Thread> findThreads(ThreadGroup threadGroup, boolean recurse, Predicate<Thread> predicate)
    Finds all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups).
    Parameters:
      `threadGroup` - the thread group.
      `recurse` - if `true` then evaluate the predicate recursively on all threads in all subgroups of the given group.
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active threads which match the given predicate and which belongs to the given thread group.
    Throws:
      `NullPointerException` - if the given group or predicate is null.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.
    Since:
      3.13.0

  - ### findThreads

    @Deprecated public static Collection<Thread> findThreads(ThreadGroup threadGroup, boolean recurse, ThreadUtils.ThreadPredicate predicate)
    Deprecated.
    Use `findThreads(ThreadGroup, boolean, Predicate)`.
    Finds all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups).
    Parameters:
      `threadGroup` - the thread group.
      `recurse` - if `true` then evaluate the predicate recursively on all threads in all subgroups of the given group.
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active threads which match the given predicate and which belongs to the given thread group.
    Throws:
      `NullPointerException` - if the given group or predicate is null.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreads

    @Deprecated public static Collection<Thread> findThreads(ThreadUtils.ThreadPredicate predicate)
    Deprecated.
    Use `findThreads(Predicate)`.
    Finds all active threads which match the given predicate.
    Parameters:
      `predicate` - the predicate.
    Returns:
      An unmodifiable `Collection` of active threads matching the given predicate.
    Throws:
      `NullPointerException` - if the predicate is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadsByName

    public static Collection<Thread> findThreadsByName(String threadName)
    Finds active threads with the specified name.
    Parameters:
      `threadName` - The thread name.
    Returns:
      The threads with the specified name or an empty collection if no such thread exists. The collection returned is always unmodifiable.
    Throws:
      `NullPointerException` - if the specified name is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadsByName

    public static Collection<Thread> findThreadsByName(String threadName, String threadGroupName)
    Finds active threads with the specified name if they belong to a thread group with the specified group name.
    Parameters:
      `threadName` - The thread name.
      `threadGroupName` - The thread group name.
    Returns:
      The threads which belongs to a thread group with the specified group name and the thread's name match the specified name, An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
    Throws:
      `NullPointerException` - if the specified thread name or group name is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### findThreadsByName

    public static Collection<Thread> findThreadsByName(String threadName, ThreadGroup threadGroup)
    Finds active threads with the specified name if they belong to a specified thread group.
    Parameters:
      `threadName` - The thread name.
      `threadGroup` - The thread group.
    Returns:
      The threads which belongs to a thread group and the thread's name match the specified name, An empty collection is returned if no such thread exists. The collection returned is always unmodifiable.
    Throws:
      `NullPointerException` - if the specified thread name or group is null.
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### getAllThreadGroups

    public static Collection<ThreadGroup> getAllThreadGroups()
    Gets all active thread groups excluding the system thread group (A thread group is active if it has been not destroyed).
    Returns:
      all thread groups excluding the system thread group. The collection returned is always unmodifiable.
    Throws:
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### getAllThreads

    public static Collection<Thread> getAllThreads()
    Gets all active threads (A thread is active if it has been started and has not yet died).
    Returns:
      all active threads. The collection returned is always unmodifiable.
    Throws:
      `SecurityException` - if the current thread cannot access the system thread group.
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### getSystemThreadGroup

    public static ThreadGroup getSystemThreadGroup()
    Gets the system thread group (sometimes also referred as "root thread group").

    This method returns null if this thread has died (been stopped).

    Returns:
      the system thread group.
    Throws:
      `SecurityException` - if the current thread cannot modify thread groups from this thread's thread group up to the system thread group.

  - ### join

    public static void join(Thread thread, Duration duration) throws InterruptedException
    Waits for the given thread to die for the given duration. Implemented using `Thread.join(long, int)`.
    Parameters:
      `thread` - The thread to join.
      `duration` - How long to wait.
    Throws:
      `InterruptedException` - if any thread has interrupted the current thread.
    Since:
      3.12.0
    See Also:
      - `Thread.join(long, int)`

  - ### sleep

    public static void sleep(Duration duration) throws InterruptedException
    Sleeps the current thread for the given duration. Implemented using `Thread.sleep(long, int)`.
    Parameters:
      `duration` - How long to sleep.
    Throws:
      `InterruptedException` - if any thread has interrupted the current thread.
    Since:
      3.12.0
    See Also:
      - `Thread.sleep(long, int)`

  - ### sleepQuietly

    public static void sleepQuietly(Duration duration)
    Sleeps for the given duration while ignoring `InterruptedException`.

    The sleep duration may be shorter than duration if we catch a `InterruptedException`.

    Parameters:
      `duration` - the length of time to sleep.
    Since:
      3.13.0