# ThreadGroup

public class **ThreadGroup** extends [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)  
implements Thread.UncaughtExceptionHandler A thread group represents a set of threads. In addition, a thread
group can also include other thread groups. The thread groups form
a tree in which every thread group except the initial thread group
has a parent.


A thread is allowed to access information about its own thread
group, but not to access information about its thread group's
parent thread group or any other thread groups.

### Public Constructor Summary

|---|---|
|   | [ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#ThreadGroup(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) name) Constructs a new thread group. |
|   | [ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#ThreadGroup(java.lang.ThreadGroup,%20java.lang.String))([ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) parent, [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) name) Creates a new thread group. |

### Public Method Summary

|---|---|
| int | [activeCount](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#activeCount())() Returns an estimate of the number of active threads in this thread group and its subgroups. |
| int | [activeGroupCount](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#activeGroupCount())() Returns an estimate of the number of active groups in this thread group and its subgroups. |
| final void | [checkAccess](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess())() Determines if the currently running thread has permission to modify this thread group. |
| final void | [destroy](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#destroy())() Destroys this thread group and all of its subgroups. |
| int | [enumerate](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#enumerate(java.lang.ThreadGroup[]))([ThreadGroup\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) list) Copies into the specified array references to every active subgroup in this thread group and its subgroups. |
| int | [enumerate](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#enumerate(java.lang.ThreadGroup[],%20boolean))([ThreadGroup\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) list, boolean recurse) Copies into the specified array references to every active subgroup in this thread group. |
| int | [enumerate](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#enumerate(java.lang.Thread[]))(Thread\[\] list) Copies into the specified array every active thread in this thread group and its subgroups. |
| int | [enumerate](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#enumerate(java.lang.Thread[],%20boolean))(Thread\[\] list, boolean recurse) Copies into the specified array every active thread in this thread group. |
| final int | [getMaxPriority](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#getMaxPriority())() Returns the maximum priority of this thread group. |
| final [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [getName](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#getName())() Returns the name of this thread group. |
| final [ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) | [getParent](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#getParent())() Returns the parent of this thread group. |
| final void | [interrupt](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#interrupt())() Interrupts all threads in this thread group. |
| final boolean | [isDaemon](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#isDaemon())() Tests if this thread group is a daemon thread group. |
| synchronized boolean | [isDestroyed](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#isDestroyed())() Tests if this thread group has been destroyed. |
| void | [list](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#list())() Prints information about this thread group to the standard output. |
| final boolean | [parentOf](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#parentOf(java.lang.ThreadGroup))([ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) g) Tests if this thread group is either the thread group argument or one of its ancestor thread groups. |
| final void | [resume](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#resume())() *This method is deprecated. This method is used solely in conjunction with Thread.suspend and ThreadGroup.suspend, both of which have been deprecated, as they are inherently deadlock-prone. See `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#suspend()` for details.* |
| final void | [setDaemon](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#setDaemon(boolean))(boolean daemon) Changes the daemon status of this thread group. |
| final void | [setMaxPriority](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#setMaxPriority(int))(int pri) Sets the maximum priority of the group. |
| final void | [stop](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#stop())() *This method is deprecated. This method is inherently unsafe. See `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#stop()` for details.* |
| final void | [suspend](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#suspend())() *This method is deprecated. This method is inherently deadlock-prone. See `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#suspend()` for details.* |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#toString())() Returns a string representation of this Thread group. |
| void | [uncaughtException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#uncaughtException(java.lang.Thread,%20java.lang.Throwable))(Thread t, [Throwable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Throwable.html) e) Called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception, and the thread does not have a specific `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.UncaughtExceptionHandler.html` installed. |

### Inherited Method Summary

From class [java.lang.Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)

|---|---|
| [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) | [clone](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#clone())() Creates and returns a copy of this `Object`. |
| boolean | [equals](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#equals(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Compares this instance with the specified object and indicates if they are equal. |
| void | [finalize](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#finalize())() Invoked when the garbage collector has detected that this instance is no longer reachable. |
| final [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> | [getClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#getClass())() Returns the unique instance of `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html` that represents this object's class. |
| int | [hashCode](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#hashCode())() Returns an integer hash code for this object. |
| final void | [notify](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notify())() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| final void | [notifyAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notifyAll())() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#toString())() Returns a string containing a concise, human-readable description of this object. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long,%20int))(long timeout, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long))(long timeout) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait())() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object. |

From interface java.lang.Thread.UncaughtExceptionHandler

|---|---|
| abstract void | uncaughtException(Thread arg0, [Throwable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Throwable.html) arg1) |

## Public Constructors

#### public
**ThreadGroup**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) name)

Constructs a new thread group. The parent of this new group is
the thread group of the currently running thread.


The `checkAccess` method of the parent thread group is
called with no arguments; this may result in a security exception.

##### Parameters

| name | the name of the new thread group. |
|---|---|

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot create a thread in the specified thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public
**ThreadGroup**
([ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) parent, [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) name)

Creates a new thread group. The parent of this new group is the
specified thread group.


The `checkAccess` method of the parent thread group is
called with no arguments; this may result in a security exception.

##### Parameters

| parent | the parent thread group. |
| name | the name of the new thread group. |
|---|---|

##### Throws

| [NullPointerException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/NullPointerException.html) | if the thread group argument is `null`. |
| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot create a thread in the specified thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

## Public Methods

#### public int
**activeCount**
()

Returns an estimate of the number of active threads in this thread
group and its subgroups. Recursively iterates over all subgroups in
this thread group.

The value returned is only an estimate because the number of
threads may change dynamically while this method traverses internal
data structures, and might be affected by the presence of certain
system threads. This method is intended primarily for debugging
and monitoring purposes.

##### Returns

- an estimate of the number of active threads in this thread group and in any other thread group that has this thread group as an ancestor

#### public int
**activeGroupCount**
()

Returns an estimate of the number of active groups in this
thread group and its subgroups. Recursively iterates over
all subgroups in this thread group.

The value returned is only an estimate because the number of
thread groups may change dynamically while this method traverses
internal data structures. This method is intended primarily for
debugging and monitoring purposes.

##### Returns

- the number of active thread groups with this thread group as an ancestor

#### public final void
**checkAccess**
()

Determines if the currently running thread has permission to
modify this thread group.


If there is a security manager, its `checkAccess` method
is called with this thread group as its argument. This may result
in throwing a `SecurityException`.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread is not allowed to access this thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityManager.html#checkAccess(java.lang.ThreadGroup)`

#### public final void
**destroy**
()

Destroys this thread group and all of its subgroups. This thread
group must be empty, indicating that all threads that had been in
this thread group have since stopped.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.

##### Throws

| [IllegalThreadStateException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalThreadStateException.html) | if the thread group is not empty or if the thread group has already been destroyed. |
| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot modify this thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public int
**enumerate**
([ThreadGroup\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) list)

Copies into the specified array references to every active
subgroup in this thread group and its subgroups.

An invocation of this method behaves in exactly the same
way as the invocation

> {@linkplain #enumerate(ThreadGroup\[\], boolean) enumerate}`(list, true)`

<br />

##### Parameters

| list | an array into which to put the list of thread groups |
|---|---|

##### Returns

- the number of thread groups put into the array

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if {@linkplain #checkAccess checkAccess} determines that the current thread cannot access this thread group |
|---|---|

#### public int
**enumerate**
([ThreadGroup\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) list, boolean recurse)

Copies into the specified array references to every active
subgroup in this thread group. If `recurse` is
`true`, this method recursively enumerates all subgroups of this
thread group and references to every active thread group in these
subgroups are also included.

An application might use the
{@linkplain #activeGroupCount activeGroupCount} method to
get an estimate of how big the array should be, however *if the array is too short to hold all the thread groups, the extra thread groups are silently ignored.* If it is critical to obtain every
active subgroup in this thread group, the caller should verify that
the returned int value is strictly less than the length of
`list`.

Due to the inherent race condition in this method, it is recommended
that the method only be used for debugging and monitoring purposes.

##### Parameters

| list | an array into which to put the list of thread groups |
| recurse | if `true`, recursively enumerate all subgroups |
|---|---|

##### Returns

- the number of thread groups put into the array

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if {@linkplain #checkAccess checkAccess} determines that the current thread cannot access this thread group |
|---|---|

#### public int
**enumerate**
(Thread\[\] list)

Copies into the specified array every active thread in this
thread group and its subgroups.

An invocation of this method behaves in exactly the same
way as the invocation

> {@linkplain #enumerate(Thread\[\], boolean) enumerate}`(list, true)`

<br />

##### Parameters

| list | an array into which to put the list of threads |
|---|---|

##### Returns

- the number of threads put into the array

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if {@linkplain #checkAccess checkAccess} determines that the current thread cannot access this thread group |
|---|---|

#### public int
**enumerate**
(Thread\[\] list, boolean recurse)

Copies into the specified array every active thread in this
thread group. If `recurse` is `true`,
this method recursively enumerates all subgroups of this
thread group and references to every active thread in these
subgroups are also included. If the array is too short to
hold all the threads, the extra threads are silently ignored.

An application might use the {@linkplain #activeCount activeCount}
method to get an estimate of how big the array should be, however
*if the array is too short to hold all the threads, the extra threads are silently ignored.* If it is critical to obtain every active
thread in this thread group, the caller should verify that the returned
int value is strictly less than the length of `list`.

Due to the inherent race condition in this method, it is recommended
that the method only be used for debugging and monitoring purposes.

##### Parameters

| list | an array into which to put the list of threads |
| recurse | if `true`, recursively enumerate all subgroups of this thread group |
|---|---|

##### Returns

- the number of threads put into the array

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if {@linkplain #checkAccess checkAccess} determines that the current thread cannot access this thread group |
|---|---|

#### public final int
**getMaxPriority**
()

Returns the maximum priority of this thread group. Threads that are
part of this group cannot have a higher priority than the maximum
priority.

##### Returns

- the maximum priority that a thread in this thread group can have.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#setMaxPriority(int)`

#### public final [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**getName**
()

Returns the name of this thread group.

##### Returns

- the name of this thread group.

#### public final [ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html)
**getParent**
()

Returns the parent of this thread group.


First, if the parent is not `null`, the
`checkAccess` method of the parent thread group is
called with no arguments; this may result in a security exception.

##### Returns

- the parent of this thread group. The top-level thread group is the only thread group whose parent is `null`.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot modify this thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/RuntimePermission.html`

#### public final void
**interrupt**
()

Interrupts all threads in this thread group.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


This method then calls the `interrupt` method on all the
threads in this thread group and in all of its subgroups.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread is not allowed to access this thread group or any of the threads in the thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#interrupt()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public final boolean
**isDaemon**
()

Tests if this thread group is a daemon thread group. A
daemon thread group is automatically destroyed when its last
thread is stopped or its last thread group is destroyed.

##### Returns

- `true` if this thread group is a daemon thread group; `false` otherwise.

#### public synchronized boolean
**isDestroyed**
()

Tests if this thread group has been destroyed.

##### Returns

- true if this object is destroyed

#### public void
**list**
()

Prints information about this thread group to the standard
output. This method is useful only for debugging.

#### public final boolean
**parentOf**
([ThreadGroup](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html) g)

Tests if this thread group is either the thread group
argument or one of its ancestor thread groups.

##### Parameters

| g | a thread group. |
|---|---|

##### Returns

- `true` if this thread group is the thread group argument or one of its ancestor thread groups; `false` otherwise.

#### public final void
**resume**
()


**This method is deprecated.**   
This method is used solely in conjunction with
Thread.suspend and ThreadGroup.suspend,
both of which have been deprecated, as they are inherently
deadlock-prone. See `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#suspend()` for details.

Resumes all threads in this thread group.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


This method then calls the `resume` method on all the
threads in this thread group and in all of its sub groups.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread is not allowed to access this thread group or any of the threads in the thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#resume()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public final void
**setDaemon**
(boolean daemon)

Changes the daemon status of this thread group.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


A daemon thread group is automatically destroyed when its last
thread is stopped or its last thread group is destroyed.

##### Parameters

| daemon | if `true`, marks this thread group as a daemon thread group; otherwise, marks this thread group as normal. |
|---|---|

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot modify this thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public final void
**setMaxPriority**
(int pri)

Sets the maximum priority of the group. Threads in the thread
group that already have a higher priority are not affected.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


If the `pri` argument is less than
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#MIN_PRIORITY` or greater than
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#MAX_PRIORITY`, it is clamped to those values.


Otherwise, the priority of this ThreadGroup object is set to the
smaller of the specified `pri` and the maximum permitted
priority of the parent of this thread group. (If this thread group
is the system thread group, which has no parent, then its maximum
priority is simply set to `pri`.) Then this method is
called recursively, with `pri` as its argument, for
every thread group that belongs to this thread group.

##### Parameters

| pri | the new priority of the thread group. |
|---|---|

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread cannot modify this thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#getMaxPriority()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public final void
**stop**
()


**This method is deprecated.**   
This method is inherently unsafe. See
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#stop()` for details.

Stops all threads in this thread group.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


This method then calls the `stop` method on all the
threads in this thread group and in all of its subgroups.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread is not allowed to access this thread group or any of the threads in the thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#stop()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public final void
**suspend**
()


**This method is deprecated.**   
This method is inherently deadlock-prone. See
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#suspend()` for details.

Suspends all threads in this thread group.


First, the `checkAccess` method of this thread group is
called with no arguments; this may result in a security exception.


This method then calls the `suspend` method on all the
threads in this thread group and in all of its subgroups.

##### Throws

| [SecurityException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html) | if the current thread is not allowed to access this thread group or any of the threads in the thread group. |
|---|---|

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#suspend()`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/SecurityException.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadGroup.html#checkAccess()`

#### public [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**toString**
()

Returns a string representation of this Thread group.

##### Returns

- a string representation of this thread group.

#### public void
**uncaughtException**
(Thread t, [Throwable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Throwable.html) e)

Called by the Java Virtual Machine when a thread in this
thread group stops because of an uncaught exception, and the thread
does not have a specific `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.UncaughtExceptionHandler.html`
installed.


The `uncaughtException` method of
`ThreadGroup` does the following:

- If this thread group has a parent thread group, the `uncaughtException` method of that parent is called with the same two arguments.
- Otherwise, this method checks to see if there is a {@linkplain Thread#getDefaultUncaughtExceptionHandler default uncaught exception handler} installed, and if so, its `uncaughtException` method is called with the same two arguments.
- Otherwise, this method determines if the `Throwable` argument is an instance of `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ThreadDeath.html`. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Thread.html#getName()` method, and a stack backtrace, using the `Throwable`'s `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Throwable.html#printStackTrace()` method, is printed to the {@linkplain System#err standard error stream}.


Applications can override this method in subclasses of
`ThreadGroup` to provide alternative handling of
uncaught exceptions.

##### Parameters

| t | the thread that is about to exit. |
| e | the uncaught exception. |
|---|---|