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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.lang3;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * 

* Helpers for {@code java.lang.Thread} and {@code java.lang.ThreadGroup}. *

*

* #ThreadSafe# *

* * @see java.lang.Thread * @see java.lang.ThreadGroup * @since 3.5 */ public class ThreadUtils { /** * Return the active thread with the specified id if it belongs to the specified thread group. * * @param threadId The thread id * @param threadGroup The thread group * @return The thread which belongs to a specified thread group and the thread's id match the specified id. * {@code null} is returned if no such thread exists * @throws IllegalArgumentException if the specified id is zero or negative or the group is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Thread findThreadById(final long threadId, final ThreadGroup threadGroup) { Validate.isTrue(threadGroup != null, "The thread group must not be null"); final Thread thread = findThreadById(threadId); if(thread != null && threadGroup.equals(thread.getThreadGroup())) { return thread; } return null; } /** * Return the active thread with the specified id if it belongs to a thread group with the specified group name. * * @param threadId The thread id * @param threadGroupName The thread group name * @return The threads which belongs to a thread group with the specified group name and the thread's id match the specified id. * {@code null} is returned if no such thread exists * @throws IllegalArgumentException if the specified id is zero or negative or the group name is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Thread findThreadById(final long threadId, final String threadGroupName) { Validate.isTrue(threadGroupName != null, "The thread group name must not be null"); final Thread thread = findThreadById(threadId); if(thread != null && thread.getThreadGroup() != null && thread.getThreadGroup().getName().equals(threadGroupName)) { return thread; } return null; } /** * Return active threads with the specified name if they belong to a specified thread group. * * @param threadName The thread name * @param threadGroup The thread group * @return The threads which belongs to a thread group and the thread's name match the specified name, * An empty collection is returned if no such thread exists. The collection returned is always unmodifiable. * @throws IllegalArgumentException if the specified thread name or group is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadsByName(final String threadName, final ThreadGroup threadGroup) { return findThreads(threadGroup, false, new NamePredicate(threadName)); } /** * Return active threads with the specified name if they belong to a thread group with the specified group name. * * @param threadName The thread name * @param threadGroupName The thread group name * @return The threads which belongs to a thread group with the specified group name and the thread's name match the specified name, * An empty collection is returned if no such thread exists. The collection returned is always unmodifiable. * @throws IllegalArgumentException if the specified thread name or group name is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadsByName(final String threadName, final String threadGroupName) { Validate.isTrue(threadName != null, "The thread name must not be null"); Validate.isTrue(threadGroupName != null, "The thread group name must not be null"); final Collection threadGroups = findThreadGroups(new NamePredicate(threadGroupName)); if(threadGroups.isEmpty()) { return Collections.emptyList(); } final Collection result = new ArrayList<>(); final NamePredicate threadNamePredicate = new NamePredicate(threadName); for(final ThreadGroup group : threadGroups) { result.addAll(findThreads(group, false, threadNamePredicate)); } return Collections.unmodifiableCollection(result); } /** * Return active thread groups with the specified group name. * * @param threadGroupName The thread group name * @return the thread groups with the specified group name or an empty collection if no such thread group exists. The collection returned is always unmodifiable. * @throws IllegalArgumentException if group name is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadGroupsByName(final String threadGroupName) { return findThreadGroups(new NamePredicate(threadGroupName)); } /** * Return all active thread groups excluding the system thread group (A thread group is active if it has been not destroyed). * * @return all thread groups excluding the system thread group. The collection returned is always unmodifiable. * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection getAllThreadGroups() { return findThreadGroups(ALWAYS_TRUE_PREDICATE); } /** * Return the system thread group (sometimes also referred as "root thread group"). * * @return the system thread group * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static ThreadGroup getSystemThreadGroup() { ThreadGroup threadGroup = Thread.currentThread().getThreadGroup(); while(threadGroup.getParent() != null) { threadGroup = threadGroup.getParent(); } return threadGroup; } /** * Return all active threads (A thread is active if it has been started and has not yet died). * * @return all active threads. The collection returned is always unmodifiable. * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection getAllThreads() { return findThreads(ALWAYS_TRUE_PREDICATE); } /** * Return active threads with the specified name. * * @param threadName The thread name * @return The threads with the specified name or an empty collection if no such thread exists. The collection returned is always unmodifiable. * @throws IllegalArgumentException if the specified name is null * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadsByName(final String threadName) { return findThreads(new NamePredicate(threadName)); } /** * Return the active thread with the specified id. * * @param threadId The thread id * @return The thread with the specified id or {@code null} if no such thread exists * @throws IllegalArgumentException if the specified id is zero or negative * @throws SecurityException * if the current thread cannot access the system thread group * * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Thread findThreadById(final long threadId) { final Collection result = findThreads(new ThreadIdPredicate(threadId)); return result.isEmpty() ? null : result.iterator().next(); } /** *

* ThreadUtils instances should NOT be constructed in standard programming. Instead, the class should be used as * {@code ThreadUtils.getAllThreads()} *

*

* This constructor is public to permit tools that require a JavaBean instance to operate. *

*/ public ThreadUtils() { super(); } /** * A predicate for selecting threads. */ //if java minimal version for lang becomes 1.8 extend this interface from java.util.function.Predicate public interface ThreadPredicate /*extends java.util.function.Predicate*/{ /** * Evaluates this predicate on the given thread. * @param thread the thread * @return {@code true} if the thread matches the predicate, otherwise {@code false} */ boolean test(Thread thread); } /** * A predicate for selecting threadgroups. */ //if java minimal version for lang becomes 1.8 extend this interface from java.util.function.Predicate public interface ThreadGroupPredicate /*extends java.util.function.Predicate*/{ /** * Evaluates this predicate on the given threadgroup. * @param threadGroup the threadgroup * @return {@code true} if the threadGroup matches the predicate, otherwise {@code false} */ boolean test(ThreadGroup threadGroup); } /** * Predicate which always returns true. */ public static final AlwaysTruePredicate ALWAYS_TRUE_PREDICATE = new AlwaysTruePredicate(); /** * A predicate implementation which always returns true. */ private static final class AlwaysTruePredicate implements ThreadPredicate, ThreadGroupPredicate{ private AlwaysTruePredicate() { } @Override public boolean test(final ThreadGroup threadGroup) { return true; } @Override public boolean test(final Thread thread) { return true; } } /** * A predicate implementation which matches a thread or threadgroup name. */ public static class NamePredicate implements ThreadPredicate, ThreadGroupPredicate { private final String name; /** * Predicate constructor * * @param name thread or threadgroup name * @throws IllegalArgumentException if the name is {@code null} */ public NamePredicate(final String name) { super(); Validate.isTrue(name != null, "The name must not be null"); this.name = name; } @Override public boolean test(final ThreadGroup threadGroup) { return threadGroup != null && threadGroup.getName().equals(name); } @Override public boolean test(final Thread thread) { return thread != null && thread.getName().equals(name); } } /** * A predicate implementation which matches a thread id. */ public static class ThreadIdPredicate implements ThreadPredicate { private final long threadId; /** * Predicate constructor * * @param threadId the threadId to match * @throws IllegalArgumentException if the threadId is zero or negative */ public ThreadIdPredicate(final long threadId) { super(); if (threadId <= 0) { throw new IllegalArgumentException("The thread id must be greater than zero"); } this.threadId = threadId; } @Override public boolean test(final Thread thread) { return thread != null && thread.getId() == threadId; } } /** * Select all active threads which match the given predicate. * * @param predicate the predicate * @return An unmodifiable {@code Collection} of active threads matching the given predicate * * @throws IllegalArgumentException if the predicate is null * @throws SecurityException * if the current thread cannot access the system thread group * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreads(final ThreadPredicate predicate){ return findThreads(getSystemThreadGroup(), true, predicate); } /** * Select all active threadgroups which match the given predicate. * * @param predicate the predicate * @return An unmodifiable {@code Collection} of active threadgroups matching the given predicate * @throws IllegalArgumentException if the predicate is null * @throws SecurityException * if the current thread cannot access the system thread group * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadGroups(final ThreadGroupPredicate predicate){ return findThreadGroups(getSystemThreadGroup(), true, predicate); } /** * Select all active threads which match the given predicate and which belongs to the given thread group (or one of its subgroups). * * @param group the thread group * @param recurse if {@code true} then evaluate the predicate recursively on all threads in all subgroups of the given group * @param predicate the predicate * @return An unmodifiable {@code Collection} of active threads which match the given predicate and which belongs to the given thread group * @throws IllegalArgumentException if the given group or predicate is null * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreads(final ThreadGroup group, final boolean recurse, final ThreadPredicate predicate) { Validate.isTrue(group != null, "The group must not be null"); Validate.isTrue(predicate != null, "The predicate must not be null"); int count = group.activeCount(); Thread[] threads; do { threads = new Thread[count + (count / 2) + 1]; //slightly grow the array size count = group.enumerate(threads, recurse); //return value of enumerate() must be strictly less than the array size according to javadoc } while (count >= threads.length); final List result = new ArrayList<>(count); for (int i = 0; i < count; ++i) { if (predicate.test(threads[i])) { result.add(threads[i]); } } return Collections.unmodifiableCollection(result); } /** * Select all active threadgroups which match the given predicate and which is a subgroup of the given thread group (or one of its subgroups). * * @param group the thread group * @param recurse if {@code true} then evaluate the predicate recursively on all threadgroups in all subgroups of the given group * @param predicate the predicate * @return An unmodifiable {@code Collection} of active threadgroups which match the given predicate and which is a subgroup of the given thread group * @throws IllegalArgumentException if the given group or predicate is null * @throws SecurityException if the current thread cannot modify * thread groups from this thread's thread group up to the system thread group */ public static Collection findThreadGroups(final ThreadGroup group, final boolean recurse, final ThreadGroupPredicate predicate){ Validate.isTrue(group != null, "The group must not be null"); Validate.isTrue(predicate != null, "The predicate must not be null"); int count = group.activeGroupCount(); ThreadGroup[] threadGroups; do { threadGroups = new ThreadGroup[count + (count / 2) + 1]; //slightly grow the array size count = group.enumerate(threadGroups, recurse); //return value of enumerate() must be strictly less than the array size according to javadoc } while(count >= threadGroups.length); final List result = new ArrayList<>(count); for(int i = 0; i < count; ++i) { if(predicate.test(threadGroups[i])) { result.add(threadGroups[i]); } } return Collections.unmodifiableCollection(result); } }




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