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/*
* This file is part of spark.
*
* Copyright (c) lucko (Luck) <luck@lucko.me>
* Copyright (c) contributors
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package me.lucko.spark.util;
import java.util.Arrays;
import java.util.Objects;
import java.util.stream.Stream;
/**
* Utility to find active threads.
*/
public final class ThreadFinder {
private static final ThreadGroup ROOT_THREAD_GROUP;
static {
ThreadGroup rootGroup = Thread.currentThread().getThreadGroup();
ThreadGroup parentGroup;
while ((parentGroup = rootGroup.getParent()) != null) {
rootGroup = parentGroup;
}
ROOT_THREAD_GROUP = rootGroup;
}
// cache the approx active count at the time of construction.
// the usages of this class are likely to be somewhat short-lived, so it's good
// enough to just cache a value on init.
private final int approxActiveCount = ROOT_THREAD_GROUP.activeCount();
/**
* Gets a stream of all known active threads.
*
* @return a stream of threads
*/
public Stream<Thread> getThreads() {
Thread[] threads = new Thread[this.approxActiveCount + 20]; // +20 to allow a bit of growth for newly created threads
while (ROOT_THREAD_GROUP.enumerate(threads, true) == threads.length) {
threads = new Thread[threads.length * 2];
}
return Arrays.stream(threads).filter(Objects::nonNull);
}
}
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