375 lines
14 KiB
Java
375 lines
14 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.commons.lang3.concurrent;
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import java.util.concurrent.Executors;
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import java.util.concurrent.ThreadFactory;
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import java.util.concurrent.atomic.AtomicLong;
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import org.apache.commons.lang3.Validate;
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/**
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* <p>
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* An implementation of the {@code ThreadFactory} interface that provides some
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* configuration options for the threads it creates.
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* </p>
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* <p>
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* A {@code ThreadFactory} is used for instance by an {@code ExecutorService} to
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* create the threads it uses for executing tasks. In many cases users do not
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* have to care about a {@code ThreadFactory} because the default one used by an
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* {@code ExecutorService} will do. However, if there are special requirements
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* for the threads, a custom {@code ThreadFactory} has to be created.
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* </p>
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* <p>
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* This class provides some frequently needed configuration options for the
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* threads it creates. These are the following:
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* </p>
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* <ul>
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* <li>A name pattern for the threads created by this factory can be specified.
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* This is often useful if an application uses multiple executor services for
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* different purposes. If the names of the threads used by these services have
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* meaningful names, log output or exception traces can be much easier to read.
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* Naming patterns are <em>format strings</em> as used by the {@code
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* String.format()} method. The string can contain the place holder {@code %d}
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* which will be replaced by the number of the current thread ({@code
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* ThreadFactoryImpl} keeps a counter of the threads it has already created).
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* For instance, the naming pattern {@code "My %d. worker thread"} will result
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* in thread names like {@code "My 1. worker thread"}, {@code
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* "My 2. worker thread"} and so on.</li>
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* <li>A flag whether the threads created by this factory should be daemon
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* threads. This can impact the exit behavior of the current Java application
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* because the JVM shuts down if there are only daemon threads running.</li>
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* <li>The priority of the thread. Here an integer value can be provided. The
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* {@code java.lang.Thread} class defines constants for valid ranges of priority
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* values.</li>
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* <li>The {@code UncaughtExceptionHandler} for the thread. This handler is
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* called if an uncaught exception occurs within the thread.</li>
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* </ul>
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* <p>
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* {@code BasicThreadFactory} wraps another thread factory which actually
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* creates new threads. The configuration options are set on the threads created
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* by the wrapped thread factory. On construction time the factory to be wrapped
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* can be specified. If none is provided, a default {@code ThreadFactory} is
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* used.
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* </p>
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* <p>
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* Instances of {@code BasicThreadFactory} are not created directly, but the
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* nested {@code Builder} class is used for this purpose. Using the builder only
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* the configuration options an application is interested in need to be set. The
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* following example shows how a {@code BasicThreadFactory} is created and
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* installed in an {@code ExecutorService}:
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* </p>
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*
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* <pre>
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* // Create a factory that produces daemon threads with a naming pattern and
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* // a priority
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* BasicThreadFactory factory = new BasicThreadFactory.Builder()
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* .namingPattern("workerthread-%d")
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* .daemon(true)
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* .priority(Thread.MAX_PRIORITY)
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* .build();
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* // Create an executor service for single-threaded execution
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* ExecutorService exec = Executors.newSingleThreadExecutor(factory);
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* </pre>
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*
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* @since 3.0
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*/
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public class BasicThreadFactory implements ThreadFactory {
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/** A counter for the threads created by this factory. */
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private final AtomicLong threadCounter;
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/** Stores the wrapped factory. */
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private final ThreadFactory wrappedFactory;
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/** Stores the uncaught exception handler. */
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private final Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
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/** Stores the naming pattern for newly created threads. */
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private final String namingPattern;
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/** Stores the priority. */
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private final Integer priority;
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/** Stores the daemon status flag. */
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private final Boolean daemon;
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/**
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* Creates a new instance of {@code ThreadFactoryImpl} and configures it
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* from the specified {@code Builder} object.
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*
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* @param builder the {@code Builder} object
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*/
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private BasicThreadFactory(final Builder builder) {
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if (builder.wrappedFactory == null) {
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wrappedFactory = Executors.defaultThreadFactory();
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} else {
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wrappedFactory = builder.wrappedFactory;
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}
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namingPattern = builder.namingPattern;
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priority = builder.priority;
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daemon = builder.daemon;
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uncaughtExceptionHandler = builder.exceptionHandler;
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threadCounter = new AtomicLong();
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}
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/**
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* Returns the wrapped {@code ThreadFactory}. This factory is used for
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* actually creating threads. This method never returns <b>null</b>. If no
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* {@code ThreadFactory} was passed when this object was created, a default
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* thread factory is returned.
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*
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* @return the wrapped {@code ThreadFactory}
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*/
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public final ThreadFactory getWrappedFactory() {
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return wrappedFactory;
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}
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/**
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* Returns the naming pattern for naming newly created threads. Result can
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* be <b>null</b> if no naming pattern was provided.
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*
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* @return the naming pattern
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*/
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public final String getNamingPattern() {
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return namingPattern;
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}
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/**
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* Returns the daemon flag. This flag determines whether newly created
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* threads should be daemon threads. If <b>true</b>, this factory object
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* calls {@code setDaemon(true)} on the newly created threads. Result can be
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* <b>null</b> if no daemon flag was provided at creation time.
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*
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* @return the daemon flag
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*/
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public final Boolean getDaemonFlag() {
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return daemon;
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}
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/**
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* Returns the priority of the threads created by this factory. Result can
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* be <b>null</b> if no priority was specified.
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*
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* @return the priority for newly created threads
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*/
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public final Integer getPriority() {
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return priority;
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}
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/**
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* Returns the {@code UncaughtExceptionHandler} for the threads created by
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* this factory. Result can be <b>null</b> if no handler was provided.
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*
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* @return the {@code UncaughtExceptionHandler}
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*/
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public final Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
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return uncaughtExceptionHandler;
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}
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/**
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* Returns the number of threads this factory has already created. This
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* class maintains an internal counter that is incremented each time the
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* {@link #newThread(Runnable)} method is invoked.
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*
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* @return the number of threads created by this factory
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*/
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public long getThreadCount() {
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return threadCounter.get();
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}
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/**
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* Creates a new thread. This implementation delegates to the wrapped
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* factory for creating the thread. Then, on the newly created thread the
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* corresponding configuration options are set.
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*
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* @param runnable the {@code Runnable} to be executed by the new thread
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* @return the newly created thread
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*/
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@Override
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public Thread newThread(final Runnable runnable) {
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final Thread thread = getWrappedFactory().newThread(runnable);
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initializeThread(thread);
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return thread;
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}
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/**
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* Initializes the specified thread. This method is called by
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* {@link #newThread(Runnable)} after a new thread has been obtained from
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* the wrapped thread factory. It initializes the thread according to the
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* options set for this factory.
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*
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* @param thread the thread to be initialized
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*/
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private void initializeThread(final Thread thread) {
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if (getNamingPattern() != null) {
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final Long count = Long.valueOf(threadCounter.incrementAndGet());
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thread.setName(String.format(getNamingPattern(), count));
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}
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if (getUncaughtExceptionHandler() != null) {
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thread.setUncaughtExceptionHandler(getUncaughtExceptionHandler());
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}
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if (getPriority() != null) {
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thread.setPriority(getPriority().intValue());
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}
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if (getDaemonFlag() != null) {
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thread.setDaemon(getDaemonFlag().booleanValue());
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}
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}
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/**
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* <p>
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* A <em>builder</em> class for creating instances of {@code
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* BasicThreadFactory}.
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* </p>
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* <p>
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* Using this builder class instances of {@code BasicThreadFactory} can be
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* created and initialized. The class provides methods that correspond to
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* the configuration options supported by {@code BasicThreadFactory}. Method
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* chaining is supported. Refer to the documentation of {@code
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* BasicThreadFactory} for a usage example.
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* </p>
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*
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*/
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public static class Builder
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implements org.apache.commons.lang3.builder.Builder<BasicThreadFactory> {
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/** The wrapped factory. */
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private ThreadFactory wrappedFactory;
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/** The uncaught exception handler. */
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private Thread.UncaughtExceptionHandler exceptionHandler;
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/** The naming pattern. */
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private String namingPattern;
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/** The priority. */
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private Integer priority;
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/** The daemon flag. */
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private Boolean daemon;
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/**
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* Sets the {@code ThreadFactory} to be wrapped by the new {@code
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* BasicThreadFactory}.
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*
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* @param factory the wrapped {@code ThreadFactory} (must not be
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* <b>null</b>)
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* @return a reference to this {@code Builder}
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* @throws NullPointerException if the passed in {@code ThreadFactory}
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* is <b>null</b>
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*/
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public Builder wrappedFactory(final ThreadFactory factory) {
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Validate.notNull(factory, "factory");
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wrappedFactory = factory;
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return this;
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}
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/**
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* Sets the naming pattern to be used by the new {@code
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* BasicThreadFactory}.
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*
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* @param pattern the naming pattern (must not be <b>null</b>)
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* @return a reference to this {@code Builder}
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* @throws NullPointerException if the naming pattern is <b>null</b>
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*/
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public Builder namingPattern(final String pattern) {
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Validate.notNull(pattern, "pattern");
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namingPattern = pattern;
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return this;
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}
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/**
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* Sets the daemon flag for the new {@code BasicThreadFactory}. If this
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* flag is set to <b>true</b> the new thread factory will create daemon
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* threads.
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*
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* @param daemon the value of the daemon flag
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* @return a reference to this {@code Builder}
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*/
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public Builder daemon(final boolean daemon) {
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this.daemon = Boolean.valueOf(daemon);
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return this;
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}
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/**
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* Sets the priority for the threads created by the new {@code
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* BasicThreadFactory}.
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*
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* @param priority the priority
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* @return a reference to this {@code Builder}
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*/
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public Builder priority(final int priority) {
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this.priority = Integer.valueOf(priority);
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return this;
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}
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/**
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* Sets the uncaught exception handler for the threads created by the
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* new {@code BasicThreadFactory}.
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*
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* @param handler the {@code UncaughtExceptionHandler} (must not be
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* <b>null</b>)
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* @return a reference to this {@code Builder}
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* @throws NullPointerException if the exception handler is <b>null</b>
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*/
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public Builder uncaughtExceptionHandler(
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final Thread.UncaughtExceptionHandler handler) {
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Validate.notNull(handler, "handler");
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exceptionHandler = handler;
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return this;
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}
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/**
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* Resets this builder. All configuration options are set to default
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* values. Note: If the {@link #build()} method was called, it is not
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* necessary to call {@code reset()} explicitly because this is done
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* automatically.
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*/
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public void reset() {
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wrappedFactory = null;
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exceptionHandler = null;
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namingPattern = null;
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priority = null;
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daemon = null;
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}
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/**
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* Creates a new {@code BasicThreadFactory} with all configuration
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* options that have been specified by calling methods on this builder.
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* After creating the factory {@link #reset()} is called.
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*
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* @return the new {@code BasicThreadFactory}
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*/
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@Override
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public BasicThreadFactory build() {
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final BasicThreadFactory factory = new BasicThreadFactory(this);
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reset();
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return factory;
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}
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}
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}
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