com.blacklocus.jres.util.DaemonThreadFactory Maven / Gradle / Ivy

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/**
 * Copyright 2013 BlackLocus
 *
 * 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.
 */
package com.blacklocus.jres.util;

import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * This is a clone of Executors.DefaultThreadFactory except that the threads it produces are always daemon threads.
 * Lingering non-daemon threads are often the cause of JVM shutdown hang. All {@link Executors} builders that use
 * the Executors.DefaultThreadFactory produce non-daemon threads which result in this behavior. All {@link Executors}
 * builders have a second form which accepts a non-default {@link ThreadFactory}, the ideal conduit to make use of
 * this DaemonThreadFactory.
 */
public class DaemonThreadFactory implements ThreadFactory {

    private static final AtomicInteger poolNumber = new AtomicInteger(1);
    private final ThreadGroup group;
    private final AtomicInteger threadNumber = new AtomicInteger(1);
    private final String namePrefix;

    public DaemonThreadFactory() {
        SecurityManager s = System.getSecurityManager();
        group = (s != null) ? s.getThreadGroup() :
                Thread.currentThread().getThreadGroup();
        namePrefix = "pool-" +
                poolNumber.getAndIncrement() +
                "-thread-";
    }

    public Thread newThread(@SuppressWarnings("NullableProblems") Runnable r) {
        Thread t = new Thread(group, r,
                namePrefix + threadNumber.getAndIncrement(),
                0);
        if (!t.isDaemon())
            t.setDaemon(true);
        if (t.getPriority() != Thread.NORM_PRIORITY)
            t.setPriority(Thread.NORM_PRIORITY);
        return t;
    }

}