Package Summary Overview Summary

### class:ThreadGroup [CHANGED]
All Implemented Interfaces: `Thread.UncaughtExceptionHandler` public class ThreadGroup extends Object 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 group has a name and maximum priority. The name is allowed to access information about its own specified when creating the group and cannot be changed. The group's maximum priority is the maximum priority for threads created in the group. It is initially inherited from the parent thread group ,but not to access information about its may be changed using the `setMaxPriority` method. A thread group 's is weakly reachable from its parent group so that it is eligible for garbage collection when there are no live threads in the group and the thread group is otherwise unreachable. Unless otherwise specified, passing a `null` argument to a constructor or any method in this class will cause a `NullPointerException` to be thrown. ## Thread groups and virtual threads The Java runtime creates a special thread group for virtual threads . This group is returned by the `Thread.getThreadGroup` method when invoked on a virtual thread. The thread group differs to other thread groups in that its maximum priority is fixed and cannot be changed with the `setMaxPriority` method. Virtual threads are not included in the estimated thread count returned by the `activeCount` method, are not enumerated by the `enumerate` method, and are not interrupted by the `interrupt` method. API Note: Thread groups provided a way in early Java releases to group threads and provide a form of job control for threads. Thread groups supported the isolation of applets and defined methods intended for diagnostic purposes. It should be rare for new applications to create ThreadGroups and interact with this API. Since: 1.0
All Implemented Interfaces: `Thread.UncaughtExceptionHandler` public class ThreadGroup extends Object 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. Since: 1.0 | All Implemented Interfaces: `Thread.UncaughtExceptionHandler` public class ThreadGroup extends Object 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 group has a name and maximum priority. The name is specified when creating the group and cannot be changed. The group's maximum priority is the maximum priority for threads created in the group. It is initially inherited from the parent thread group but may be changed using the `setMaxPriority` method. A thread group is weakly reachable from its parent group so that it is eligible for garbage collection when there are no live threads in the group and the thread group is otherwise unreachable. Unless otherwise specified, passing a `null` argument to a constructor or method in this class will cause a `NullPointerException` to be thrown. ## Thread groups and virtual threads The Java runtime creates a special thread group for virtual threads . This group is returned by the `Thread.getThreadGroup` method when invoked on a virtual thread. The thread group differs to other thread groups in that its maximum priority is fixed and cannot be changed with the `setMaxPriority` method. Virtual threads are not included in the estimated thread count returned by the `activeCount` method, are not enumerated by the `enumerate` method, and are not interrupted by the `interrupt` method. API Note: Thread groups provided a way in early Java releases to group threads and provide a form of job control for threads. Thread groups supported the isolation of applets and defined methods intended for diagnostic purposes. It should be rare for new applications to create ThreadGroups and interact with this API. Since: 1.0

### constructor:ThreadGroup(java.lang.String) [CHANGED]
### ThreadGroup public ThreadGroup (String 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., can be `null` Throws: `SecurityException` - if the current thread cannot create a thread in the specified thread group. Since: 1.0 See Also: `checkAccess()`
### ThreadGroup public ThreadGroup (String 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` - if the current thread cannot create a thread in the specified thread group. Since: 1.0 See Also: `checkAccess()` | ### ThreadGroup public ThreadGroup (String 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, can be `null` Throws: `SecurityException` - if the current thread cannot create a thread in the specified thread group. See Also: `checkAccess()`

### constructor:ThreadGroup(java.lang.ThreadGroup,java.lang.String) [CHANGED]
### ThreadGroup public ThreadGroup (ThreadGroup parent, String 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., can be `null` Throws: `` `NullPointerException` - if the thread group argument is `null`. SecurityException - if the current thread cannot create a thread in the specified thread group. Since: 1.0 See Also:`SecurityException` `checkAccess()`
### ThreadGroup public ThreadGroup (ThreadGroup parent, String 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` - if the thread group argument is `null`. `SecurityException` - if the current thread cannot create a thread in the specified thread group. Since: 1.0 See Also: `SecurityException` `checkAccess()` | ### ThreadGroup public ThreadGroup (ThreadGroup parent, String 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, can be `null` Throws: `SecurityException` - if the current thread cannot create a thread in the specified thread group. See Also: `checkAccess()`

### method:getName() [CHANGED]
### getName public final String getName() Returns the name of this thread group. Returns: the name of this thread group. Since: 1.0 , may be `null`
### getName public final String getName() Returns the name of this thread group. Returns: the name of this thread group. Since: 1.0 | ### getName public final String getName() Returns the name of this thread group. Returns: the name of this thread group, may be `null`

### method:getParent() [CHANGED]
### getParent public final ThreadGroup 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` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `checkAccess()` `SecurityException` `RuntimePermission`
### getParent public final ThreadGroup 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` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `checkAccess()` `SecurityException` `RuntimePermission` | ### getParent public final ThreadGroup 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` - if the current thread cannot modify this thread group. See Also: `checkAccess()` `SecurityException` `RuntimePermission`

### method:getMaxPriority() [CHANGED]
### getMaxPriority 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 This is the maximum priority for new threads created in the thread group. Returns: the maximum priority that a thread for new threads created in this the thread group can have. Since: 1.0 See Also: `setMaxPriority(int)`
### getMaxPriority 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. Since: 1.0 See Also: `setMaxPriority(int)` | ### getMaxPriority public final int getMaxPriority() Returns the maximum priority of this thread group. This is the maximum priority for new threads created in the thread group. Returns: the maximum priority for new threads created in the thread group See Also: `setMaxPriority(int)`

### method:isDaemon() [CHANGED]
### isDaemon @Deprecated(since="16", forRemoval=true) public final boolean isDaemon() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed. The ability to explicitly or automatically destroy a thread group, and This method originally indicated if the concept of daemonthread group , will be removed in is a future release.Tests if this daemon thread group that is a automatically destroyed when its last thread terminates. The concept of daemon thread group no longer exists. A daemonthread group is automatically destroyed eligible to be GC'ed when its last thread there are no live threads in the group and it is stopped or its last otherwise unreachable. Returns the daemon status of this thread group. The daemon status is destroyed not used for anything. Returns: `true` if the daemon status of this thread group is a daemon thread group; `false` otherwise. Since: 1.0
### isDaemon @Deprecated(since="16", forRemoval=true) public final boolean isDaemon() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed. The ability to explicitly or automatically destroy a thread group, and the concept of daemon thread group, will be removed in a future release. 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. Since: 1.0 | ### isDaemon @Deprecated(since="16", forRemoval=true) public final boolean isDaemon() Deprecated, for removal: This API element is subject to removal in a future version. This method originally indicated if the thread group is a daemon thread group that is automatically destroyed when its last thread terminates. The concept of daemon thread group no longer exists. A thread group is eligible to be GC'ed when there are no live threads in the group and it is otherwise unreachable. Returns the daemon status of this thread group. The daemon status is not used for anything. Returns: the daemon status of this thread group

### method:isDestroyed() [CHANGED]
### isDestroyed @Deprecated(since="16", forRemoval=true) public boolean isDestroyed() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup This method originally indicated if the thread group is inherently flawed destroyed. The ability to explicitly or automaticallydestroy a thread group and the concept of a destroyed thread group will no longer exists. A thread group is eligible to be removed GC'ed when there are no live threads in a future release.Tests if this thread the group has been destroyed and it is otherwise unreachable. Returns false. Returns: true if this object is destroyed false Since: 1.1
### isDestroyed @Deprecated(since="16", forRemoval=true) public boolean isDestroyed() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed. The ability to explicitly or automatically destroy a thread group will be removed in a future release. Tests if this thread group has been destroyed. Returns: true if this object is destroyed Since: 1.1 | ### isDestroyed @Deprecated(since="16", forRemoval=true) public boolean isDestroyed() Deprecated, for removal: This API element is subject to removal in a future version. This method originally indicated if the thread group is destroyed. The ability to destroy a thread group and the concept of a destroyed thread group no longer exists. A thread group is eligible to be GC'ed when there are no live threads in the group and it is otherwise unreachable. Returns false. Returns: false Since: 1.1

### method:setDaemon(boolean) [CHANGED]
### setDaemon @Deprecated(since="16", forRemoval=true) public final void setDaemon (boolean daemon) Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying This method originally configured whether the thread group is a ThreadGroup daemon thread group that is inherently flawed automatically destroyed when its last thread terminates. The ability to explicitly or automatically destroy a thread group, and theconcept of daemon thread group , will no longer exists. A thread group is eligible to be removed GC'ed when there are no live threads in a future release.Changes the group and it is otherwise unreachable. Sets the daemon status of this thread group. The daemon status is not used for anything. 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 the daemon thread group; otherwise, marks this thread group as normal.status Throws: `SecurityException` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `SecurityException` `checkAccess()`
### setDaemon @Deprecated(since="16", forRemoval=true) public final void setDaemon (boolean daemon) Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed. The ability to explicitly or automatically destroy a thread group, and the concept of daemon thread group, will be removed in a future release. 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` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `SecurityException` `checkAccess()` | ### setDaemon @Deprecated(since="16", forRemoval=true) public final void setDaemon (boolean daemon) Deprecated, for removal: This API element is subject to removal in a future version. This method originally configured whether the thread group is a daemon thread group that is automatically destroyed when its last thread terminates. The concept of daemon thread group no longer exists. A thread group is eligible to be GC'ed when there are no live threads in the group and it is otherwise unreachable. Sets the daemon status of this thread group. The daemon status is not used for anything. First, the `checkAccess` method of this thread group is called with no arguments; this may result in a security exception. Parameters: `daemon` - the daemon status Throws: `SecurityException` - if the current thread cannot modify this thread group. See Also: `SecurityException` `checkAccess()`

### method:setMaxPriority(int) [CHANGED]
### setMaxPriority public final void setMaxPriority (int pri) Sets the maximum priority of the group. The maximum priority of the ThreadGroup for virtual threads is not changed by this method (the new priority is ignored). Threads in the thread group (or subgroups) that already have a higher priority are not affected by this method. 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 `Thread.MIN_PRIORITY` or greater than `Thread.MAX_PRIORITY`, the maximum priority of the group remains unchanged. 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` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `getMaxPriority()` `SecurityException` `checkAccess()`
### setMaxPriority 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 `Thread.MIN_PRIORITY` or greater than `Thread.MAX_PRIORITY`, the maximum priority of the group remains unchanged. 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` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `getMaxPriority()` `SecurityException` `checkAccess()` | ### setMaxPriority public final void setMaxPriority (int pri) Sets the maximum priority of the group. The maximum priority of the ThreadGroup for virtual threads is not changed by this method (the new priority is ignored). Threads in the thread group (or subgroups) that already have a higher priority are not affected by this method. 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 `Thread.MIN_PRIORITY` or greater than `Thread.MAX_PRIORITY`, the maximum priority of the group remains unchanged. 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` - if the current thread cannot modify this thread group. See Also: `getMaxPriority()` `SecurityException` `checkAccess()`

### method:parentOf(java.lang.ThreadGroup) [CHANGED]
### parentOf public final boolean parentOf (ThreadGroup g) Tests if this thread group is either the thread group argument or one of its ancestor thread groups. Parameters: `g` - a thread group., can be `null` Returns: `true` if this thread group is the thread group argument or one of its ancestor thread groups; `false` otherwise. Since: 1.0
### parentOf public final boolean parentOf (ThreadGroup 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. Since: 1.0 | ### parentOf public final boolean parentOf (ThreadGroup g) Tests if this thread group is either the thread group argument or one of its ancestor thread groups. Parameters: `g` - a thread group, can be `null` Returns: `true` if this thread group is the thread group argument or one of its ancestor thread groups; `false` otherwise.

### method:checkAccess() [CHANGED]
### checkAccess @Deprecated(since="17", forRemoval=true) public final void checkAccess() Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager , which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` - if the current thread is not allowed to access this thread group. Since: 1.0 See Also: `SecurityManager.checkAccess(java.lang.ThreadGroup)`
### checkAccess @Deprecated(since="17", forRemoval=true) public final void checkAccess() Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager , which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` - if the current thread is not allowed to access this thread group. Since: 1.0 See Also: `SecurityManager.checkAccess(java.lang.ThreadGroup)` | ### checkAccess @Deprecated(since="17", forRemoval=true) public final void checkAccess() Deprecated, for removal: This API element is subject to removal in a future version. This method is only useful in conjunction with the Security Manager , which is deprecated and subject to removal in a future release. Consequently, this method is also deprecated and subject to removal. There is no replacement for the Security Manager or this method. 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` - if the current thread is not allowed to access this thread group. See Also: `SecurityManager.checkAccess(java.lang.ThreadGroup)`

### method:activeCount() [CHANGED]
### activeCount public int activeCount() Returns an estimate of the number of active live platform threads in this thread group and its subgroups. Recursively Virtual threads are not included in the estimate. This method 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 live threads in this thread group and in any other thread group that has this thread group as an ancestor Since: 1.0
### activeCount 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 Since: 1.0 | ### activeCount public int activeCount() Returns an estimate of the number of live platform threads in this thread group and its subgroups. Virtual threads are not included in the estimate. This method 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 live threads in this thread group and in any other thread group that has this thread group as an ancestor

### method:enumerate(java.lang.Thread[]) [CHANGED]
### enumerate public int enumerate (Thread[] list) Copies into the specified array every active live platform thread in this thread group and its subgroups. Virtual threads are not enumerated by this method. An invocation of this method behaves in exactly the same way as the invocation enumerate`(list, true)` Parameters: `list` - an array into which to put the list of threads Returns: the number of threads put into the array Throws: `SecurityException` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0
### enumerate 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 enumerate`(list, true)` Parameters: `list` - an array into which to put the list of threads Returns: the number of threads put into the array Throws: `SecurityException` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0 | ### enumerate public int enumerate (Thread[] list) Copies into the specified array every live platform thread in this thread group and its subgroups. Virtual threads are not enumerated by this method. An invocation of this method behaves in exactly the same way as the invocation enumerate`(list, true)` Parameters: `list` - an array into which to put the list of threads Returns: the number of threads put into the array Throws: `SecurityException` - if checkAccess determines that the current thread cannot access this thread group

### method:enumerate(java.lang.Thread[],boolean) [CHANGED]
### enumerate public int enumerate (Thread[] list, boolean recurse) Copies into the specified array every active live platform thread in this thread group. Virtual threads are not enumerated by this method. If `recurse` is `true`, this method recursively enumerates all subgroups of this thread group and references to every active live platform 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 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 live 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0
### enumerate 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 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0 | ### enumerate public int enumerate (Thread[] list, boolean recurse) Copies into the specified array every live platform thread in this thread group. Virtual threads are not enumerated by this method. If `recurse` is `true`, this method recursively enumerates all subgroups of this thread group and references to every live platform 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 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 live 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` - if checkAccess determines that the current thread cannot access this thread group

### method:activeGroupCount() [CHANGED]
### activeGroupCount public int activeGroupCount() Returns an estimate of the number of activegroups 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 activethread groups with this thread group as an ancestor Since: 1.0
### activeGroupCount 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 Since: 1.0 | ### activeGroupCount public int activeGroupCount() Returns an estimate of the number of 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 thread groups with this thread group as an ancestor

### method:enumerate(java.lang.ThreadGroup[]) [CHANGED]
### enumerate public int enumerate (ThreadGroup[] list) Copies into the specified array references to every activesubgroup in this thread group and its subgroups. An invocation of this method behaves in exactly the same way as the invocation enumerate`(list, true)` 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0
### enumerate public int enumerate (ThreadGroup[] 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 enumerate`(list, true)` 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0 | ### enumerate public int enumerate (ThreadGroup[] list) Copies into the specified array references to every subgroup in this thread group and its subgroups. An invocation of this method behaves in exactly the same way as the invocation enumerate`(list, true)` 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` - if checkAccess determines that the current thread cannot access this thread group

### method:enumerate(java.lang.ThreadGroup[],boolean) [CHANGED]
### enumerate public int enumerate (ThreadGroup[] list, boolean recurse) Copies into the specified array references to every activesubgroup in this thread group. If `recurse` is `true`, this method recursively enumerates all subgroups of this thread group and references to every activethread group in these subgroups are also included. An application might use the 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 activesubgroup 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0
### enumerate public int enumerate (ThreadGroup[] 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 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` - if checkAccess determines that the current thread cannot access this thread group Since: 1.0 | ### enumerate public int enumerate (ThreadGroup[] list, boolean recurse) Copies into the specified array references to every subgroup in this thread group. If `recurse` is `true`, this method recursively enumerates all subgroups of this thread group and references to every thread group in these subgroups are also included. An application might use the 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 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` - if checkAccess determines that the current thread cannot access this thread group

### method:stop() [CHANGED]
### stop @Deprecated(since="1.2", forRemoval=true) public final void stop() Deprecated, for removal: This API element is subject to removal in a future version. This method is inherently unsafe. SeeThread.was originally specified to stop () for details.Stopsall threads in this the 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 It was inherently unsafe. Throws `: `SecurityException` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `SecurityException` `Thread.stop()` `checkAccess()` UnsupportedOperationException` .
### stop @Deprecated(since="1.2", forRemoval=true) public final void stop() Deprecated, for removal: This API element is subject to removal in a future version. This method is inherently unsafe. See `Thread.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` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `SecurityException` `Thread.stop()` `checkAccess()` | ### stop @Deprecated(since="1.2", forRemoval=true) public final void stop() Deprecated, for removal: This API element is subject to removal in a future version. This method was originally specified to stop all threads in the thread group. It was inherently unsafe. Throws `UnsupportedOperationException`.

### method:interrupt() [CHANGED]
### interrupt 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 live platform threads in this thread group and in all ofits subgroups. Throws: `SecurityException` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.2 See Also: `Thread.interrupt()` `SecurityException` `checkAccess()`
### interrupt 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` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.2 See Also: `Thread.interrupt()` `SecurityException` `checkAccess()` | ### interrupt public final void interrupt() Interrupts all live platform threads in this thread group and its subgroups. Throws: `SecurityException` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.2 See Also: `Thread.interrupt()` `SecurityException` `checkAccess()`

### method:suspend() [CHANGED]
### suspend @Deprecated(since="1.2", forRemoval=true) public final void suspend() Deprecated, for removal: This API element is subject to removal in a future version. This method is inherently deadlock-prone. SeeThread.was originally specified to suspend () for details.Suspendsall threads in this thread group. First, the `checkAccess` method of this thread group is called with no arguments; this may resultin a security exception. This method then callsthe `suspend` method on all the threads in thisthread group and in all of its subgroups. Throws `: `SecurityException` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `Thread.suspend()` `SecurityException` `checkAccess()` UnsupportedOperationException` .
### suspend @Deprecated(since="1.2", forRemoval=true) public final void suspend() Deprecated, for removal: This API element is subject to removal in a future version. This method is inherently deadlock-prone. See `Thread.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` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `Thread.suspend()` `SecurityException` `checkAccess()` | ### suspend @Deprecated(since="1.2", forRemoval=true) public final void suspend() Deprecated, for removal: This API element is subject to removal in a future version. This method was originally specified to suspend all threads in the thread group. Throws `UnsupportedOperationException`.

### method:resume() [CHANGED]
### resume @Deprecated(since="1.2", forRemoval=true) public final void resume() Deprecated, for removal: This API element is subject to removal in a future version. 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 `Thread.suspend()` for details.Resumes was originally specified to resume all threads in this thread group. First,the `checkAccess` method of thisthread 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` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `SecurityException` `Thread.resume()` `checkAccess()` UnsupportedOperationException` .
### resume @Deprecated(since="1.2", forRemoval=true) public final void resume() Deprecated, for removal: This API element is subject to removal in a future version. 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 `Thread.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` - if the current thread is not allowed to access this thread group or any of the threads in the thread group. Since: 1.0 See Also: `SecurityException` `Thread.resume()` `checkAccess()` | ### resume @Deprecated(since="1.2", forRemoval=true) public final void resume() Deprecated, for removal: This API element is subject to removal in a future version. This method was originally specified to resume all threads in the thread group. Throws `UnsupportedOperationException`.

### method:destroy() [CHANGED]
### destroy @Deprecated(since="16", forRemoval=true) public final void destroy() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed This method was originally specified to destroy an empty thread group. The ability to explicitly or automaticallydestroy a thread group will be removed in a future release.Destroys this no longer exists. A thread group and all of its subgroups. This thread group must is eligible to be empty, indicating that all GC'ed when there are no live 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 resultin a security exception. Throws: `IllegalThreadStateException` - ifthe threadgroup and it is not empty or if the thread group has already been destroyed. `SecurityException` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `checkAccess()` otherwise unreachable. Does nothing.
### destroy @Deprecated(since="16", forRemoval=true) public final void destroy() Deprecated, for removal: This API element is subject to removal in a future version. The API and mechanism for destroying a ThreadGroup is inherently flawed. The ability to explicitly or automatically destroy a thread group will be removed in a future release. 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` - if the thread group is not empty or if the thread group has already been destroyed. `SecurityException` - if the current thread cannot modify this thread group. Since: 1.0 See Also: `checkAccess()` | ### destroy @Deprecated(since="16", forRemoval=true) public final void destroy() Deprecated, for removal: This API element is subject to removal in a future version. This method was originally specified to destroy an empty thread group. The ability to explicitly destroy a thread group no longer exists. A thread group is eligible to be GC'ed when there are no live threads in the group and it is otherwise unreachable. Does nothing.

### method:list() [CHANGED]
### list public void list() Prints information about this thread group to the standard output. This method is useful only for debugging. Since: 1.0
### list public void list() Prints information about this thread group to the standard output. This method is useful only for debugging. Since: 1.0 | ### list public void list() Prints information about this thread group to the standard output. This method is useful only for debugging.

### method:uncaughtException(java.lang.Thread,java.lang.Throwable) [CHANGED]
### uncaughtException public void uncaughtException (Thread t, Throwable 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 `Thread.UncaughtExceptionHandler` 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 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 `ThreadDeath`. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's `getName` method, and a stack backtrace, using the `Throwable`'s `printStackTrace` method, is printed to the standard error stream . Applications can override this method in subclasses of `ThreadGroup` to provide alternative handling of uncaught exceptions. Specified by: `uncaughtException` in interface `Thread.UncaughtExceptionHandler` Parameters: `t` - the thread that is about to exit. `e` - the uncaught exception. Since: 1.0
### uncaughtException public void uncaughtException (Thread t, Throwable 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 `Thread.UncaughtExceptionHandler` 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 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 `ThreadDeath`. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's `getName` method, and a stack backtrace, using the `Throwable`'s `printStackTrace` method, is printed to the standard error stream . Applications can override this method in subclasses of `ThreadGroup` to provide alternative handling of uncaught exceptions. Specified by: `uncaughtException` in interface `Thread.UncaughtExceptionHandler` Parameters: `t` - the thread that is about to exit. `e` - the uncaught exception. Since: 1.0 | ### uncaughtException public void uncaughtException (Thread t, Throwable 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 `Thread.UncaughtExceptionHandler` 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 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 `ThreadDeath`. If so, nothing special is done. Otherwise, a message containing the thread's name, as returned from the thread's `getName` method, and a stack backtrace, using the `Throwable`'s `printStackTrace` method, is printed to the standard error stream . Applications can override this method in subclasses of `ThreadGroup` to provide alternative handling of uncaught exceptions. Specified by: `uncaughtException` in interface `Thread.UncaughtExceptionHandler` Parameters: `t` - the thread that is about to exit. `e` - the uncaught exception.

### method:allowThreadSuspension(boolean) [CHANGED]
### allowThreadSuspension @Deprecated(since="1.2", forRemoval=true) public boolean allowThreadSuspension (boolean b) Deprecated, for removal: This API element is subject to removal in a future version. The definition of this call depends on `suspend()`, which is deprecated. Further, the behavior of this call This method was originally intended for controlling suspension in low memory conditions. It was never specified. Used by VM to control lowmem implicit suspension Does nothing. Parameters: `b` - boolean to allow or disallow suspension ignored Returns: true on success false Since: 1.1
### allowThreadSuspension @Deprecated(since="1.2", forRemoval=true) public boolean allowThreadSuspension (boolean b) Deprecated, for removal: This API element is subject to removal in a future version. The definition of this call depends on `suspend()`, which is deprecated. Further, the behavior of this call was never specified. Used by VM to control lowmem implicit suspension. Parameters: `b` - boolean to allow or disallow suspension Returns: true on success Since: 1.1 | ### allowThreadSuspension @Deprecated(since="1.2", forRemoval=true) public boolean allowThreadSuspension (boolean b) Deprecated, for removal: This API element is subject to removal in a future version. This method was originally intended for controlling suspension in low memory conditions. It was never specified. Does nothing. Parameters: `b` - ignored Returns: false Since: 1.1

### method:toString() [CHANGED]
### toString public String toString() Returns a string representation of this Thread group. Overrides: `toString` in class `Object` Returns: a string representation of this thread group. Since: 1.0
### toString public String toString() Returns a string representation of this Thread group. Overrides: `toString` in class `Object` Returns: a string representation of this thread group. Since: 1.0 | ### toString public String toString() Returns a string representation of this Thread group. Overrides: `toString` in class `Object` Returns: a string representation of this thread group.