com.cloudhopper.commons.util.ThreadUtil Maven / Gradle / Ivy
package com.cloudhopper.commons.util;
/*
* #%L
* ch-commons-util
* %%
* Copyright (C) 2012 Cloudhopper by Twitter
* %%
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;
import java.util.ArrayList;
/**
* A utility class for working with threads in a JVM.
*
* Some of these methods were obtained here:
* http://nadeausoftware.com/articles/2008/04/java_tip_how_list_and_find_threads_and_thread_groups#Gettingalistofallthreads
*
* @author joelauer (twitter: @jjlauer or http://twitter.com/jjlauer)
*/
public class ThreadUtil {
/**
* Gets the "root" thread group for the entire JVM. Internally, first get
* the current thread and its thread group. Then get its parent group, then
* its parent group, and on up until you find a group with a null parent.
* That's the root ThreadGroup. Since the same root thread group is used
* for the life of the JVM, you can safely cache it for faster future use.
* @return The root thread group for the JVM
*/
static public ThreadGroup getRootThreadGroup() {
ThreadGroup tg = Thread.currentThread().getThreadGroup();
ThreadGroup ptg;
while ((ptg = tg.getParent()) != null)
tg = ptg;
return tg;
}
/**
* Gets all threads in the JVM. This is really a snapshot of all threads
* at the time this method is called.
* @return An array of all threads currently running in the JVM.
*/
static public Thread[] getAllThreads() {
final ThreadGroup root = getRootThreadGroup();
final ThreadMXBean thbean = ManagementFactory.getThreadMXBean();
int nAlloc = thbean.getThreadCount();
int n = 0;
Thread[] threads;
do {
nAlloc *= 2;
threads = new Thread[nAlloc];
n = root.enumerate(threads, true);
} while (n == nAlloc);
return java.util.Arrays.copyOf(threads, n);
}
/**
* Gets a thread by its assigned ID. Internally, this method calls
* getAllThreads() so be careful to only call this method once and cache
* your result.
* @param id The thread ID
* @return The thread with this ID or null if none were found
*/
static public Thread getThread(final long id) {
final Thread[] threads = getAllThreads();
for (Thread thread : threads)
if (thread.getId() == id)
return thread;
return null;
}
/**
* Gets all threads if its name matches a regular expression. For example,
* using a regex of "main" will execute a case-sensitive match for threads
* with the exact name of "main". A regex of ".*main.*" will execute a
* case sensitive match for threads with "main" anywhere in their name. A
* regex of "(?i).*main.*" will execute a case insensitive match of any
* thread that has "main" in its name.
* @param regex The regular expression to use when matching a threads name.
* Same rules apply as String.matches() method.
* @return An array (will not be null) of all matching threads. An empty
* array will be returned if no threads match.
*/
static public Thread[] getAllThreadsMatching(final String regex) {
if (regex == null)
throw new NullPointerException("Null thread name regex");
final Thread[] threads = getAllThreads();
ArrayList matchingThreads = new ArrayList();
for (Thread thread : threads) {
if (thread.getName().matches(regex)) {
matchingThreads.add(thread);
}
}
return matchingThreads.toArray(new Thread[0]);
}
}