Java tutorial
//package com.java2s; /* * Copyright (c) 2009-2013 GreenVulcano ESB Open Source Project. All rights * reserved. * * This file is part of GreenVulcano ESB. * * GreenVulcano ESB is free software: you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by the * Free Software Foundation, either version 3 of the License, or (at your * option) any later version. * * GreenVulcano ESB is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License * for more details. * * You should have received a copy of the GNU Lesser General Public License * along with GreenVulcano ESB. If not, see <http://www.gnu.org/licenses/>. */ public class Main { /** * The root thread group saved on the first search for it. The root group * doesn't change for the life of the JVM, so once found there is no need to * find it again. */ private static ThreadGroup rootThreadGroup = null; /** * Get the thread group with the given name. A null is returned if no such * group is found. If more than one group has the same name, the first one * found is returned. * * @param name * the thread group name to search for * @return the thread group, or null if not found * @throws NullPointerException * if the name is null */ public static ThreadGroup getThreadGroup(final String name) { if (name == null) { throw new NullPointerException("Null name"); } final ThreadGroup[] groups = getAllThreadGroups(); for (ThreadGroup group : groups) { if (group.getName().equals(name)) return group; } return null; } /** * Get a list of all thread groups. Since there is always at least one * thread group (the root), this method never returns a null or empty array. * * @return an array of thread groups */ public static ThreadGroup[] getAllThreadGroups() { final ThreadGroup root = getRootThreadGroup(); int nAlloc = root.activeGroupCount(); int n = 0; ThreadGroup[] groups = null; do { nAlloc *= 2; groups = new ThreadGroup[nAlloc]; n = root.enumerate(groups, true); } while (n == nAlloc); ThreadGroup[] allGroups = new ThreadGroup[n + 1]; allGroups[0] = root; System.arraycopy(groups, 0, allGroups, 1, n); return allGroups; } /** * Get the root thread group in the thread group tree. Since there is always * a root thread group, this method never returns null. * * @return the root thread group */ public static ThreadGroup getRootThreadGroup() { if (rootThreadGroup != null) { return rootThreadGroup; } ThreadGroup tg = Thread.currentThread().getThreadGroup(); ThreadGroup ptg; while ((ptg = tg.getParent()) != null) { tg = ptg; } rootThreadGroup = tg; return tg; } }