20.21

java.lang.ThreadGroup

THE PACKAGE JAVA.LANG

20.21 The Class

java.lang.ThreadGroup

A thread group is a set of threads and thread groups. Every thread belongs to

exactly one thread group, and every thread group but one (called the  system

thread group ) belongs to some other thread group. Thus thread groups form a

tree with the system thread group at the root.

Thread groups provide a way to manage threads and to impose security

boundaries; for example, a thread may always create a new thread within its own

thread group, but creating a thread in another thread group requires the approval

of the security manager ( 20.17), as does the creation of a new thread group.

public class ThreadGroup {

public ThreadGroup(String name)

throws SecurityException;

public ThreadGroup(ThreadGroup parent, String name)

throws NullPointerExpression, SecurityException,

IllegalThreadStateException;

public String toString();

public final void checkAccess();

public final String getName();

public final ThreadGroup getParent();

public final boolean parentOf(ThreadGroup g);

public final void stop()

throws SecurityException;

public final void suspend()

throws SecurityException;

public final void resume()

throws SecurityException;

public final void destroy()

throws SecurityException, IllegalThreadStateException;

public final int getMaxPriority();

public final void setMaxPriority(int newMaxPriority)

throws SecurityException, IllegalArgumentException;

public final boolean isDaemon();

public final void setDaemon(boolean daemon)

throws SecurityException;

public int threadsCount();

public int allThreadsCount();

public int groupsCount();

public int allGroupsCount();

public Thread[] threads();

public Thread[] allThreads();

public ThreadGroup[] groups();

public ThreadGroup[] allGroups();

602