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From CodingFabian <...@git.apache.org>
Subject [GitHub] commons-lang pull request: Add ThreadUtils (2nd PR)
Date Mon, 04 May 2015 19:09:14 GMT
Github user CodingFabian commented on a diff in the pull request:

    https://github.com/apache/commons-lang/pull/78#discussion_r29613233
  
    --- Diff: src/main/java/org/apache/commons/lang3/ThreadUtils.java ---
    @@ -0,0 +1,461 @@
    +/*
    + * 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;
    +
    +/**
    + * <p>
    + * Helpers for {@code java.lang.Thread} and {@code java.lang.ThreadGroup}.
    + * </p>
    + * <p>
    + * #ThreadSafe#
    + * </p>
    + *
    + * @see java.lang.Thread
    + * @see java.lang.ThreadGroup
    + * @since 3.5
    + * @version $Id$
    + */
    +public class ThreadUtils {
    +
    +    /**
    +     * Return the active thread with the specified id if it belong's 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)
{
    +        if (threadGroup == null) {
    +            throw new IllegalArgumentException("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 belong's 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)
{
    +        if (threadGroupName == null) {
    +            throw new IllegalArgumentException("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 threadGroupName 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<Thread> 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<Thread> findThreadsByName(final String threadName,
final String threadGroupName) {
    +        if (threadName == null) {
    +            throw new IllegalArgumentException("The thread name must not be null");
    +        }
    +        if (threadGroupName == null) {
    +            throw new IllegalArgumentException("The thread group name must not be null");
    +        }
    +
    +        final Collection<Thread> result = new ArrayList<Thread>();
    +        NamePredicate threadNamePredicate = null;
    +        for(final ThreadGroup group : findThreadGroups(new NamePredicate(threadGroupName)))
{
    +            result.addAll(findThreads(group, false, threadNamePredicate==null?(threadNamePredicate=new
NamePredicate(threadName)):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<ThreadGroup> 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<ThreadGroup> 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<Thread> 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<Thread> 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<Thread> result = findThreads(new ThreadIdPredicate(threadId));
    +
    +        if(result.isEmpty()) {
    +            return null;
    +        } else {
    +            return result.iterator().next();
    +        }
    +
    +    }
    +
    +    /**
    +     * <p>
    +     * ThreadUtils instances should NOT be constructed in standard programming. Instead,
the class should be used as
    +     * {@code ThreadUtils.getAllThreads()}
    +     * </p>
    +     * <p>
    +     * This constructor is public to permit tools that require a JavaBean instance to
operate.
    +     * </p>
    +     */
    +    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 static interface ThreadPredicate /*extends java.util.function.Predicate<Thread>*/{
    +
    +        /**
    +         * 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 static interface ThreadGroupPredicate /*extends java.util.function.Predicate<ThreadGroup>*/{
    +        
    +        /**
    +         * 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 final static class AlwaysTruePredicate implements ThreadPredicate, ThreadGroupPredicate{
    +
    +        private AlwaysTruePredicate() {
    +        }
    +
    +        @Override
    +        public boolean test(@SuppressWarnings("unused") final ThreadGroup threadGroup)
{
    +            return true;
    +        }
    +
    +        @Override
    +        public boolean test(@SuppressWarnings("unused") 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();
    +            if (name == null) {
    +                throw new IllegalArgumentException("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<Thread> findThreads(final ThreadPredicate predicate){
    +        return findThreads(getSystemThreadGroup(), true, predicate);
    +    }
    +
    +    /**
    +     * Select all active threadgroups which match the given predicate.
    +     * 
    +     * @param 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<ThreadGroup> 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<Thread> findThreads(final ThreadGroup group, final
boolean recurse, final ThreadPredicate predicate) {
    +        if (group == null) {
    +            throw new IllegalArgumentException("The group must not be null");
    +        }
    +        if (predicate == null) {
    +            throw new IllegalArgumentException("The predicate must not be null");
    +        }
    +
    +        int count = group.activeCount();
    +        Thread[] threads;
    +        do {
    +            threads = new Thread[count + (count >> 1) + 1];
    +            count = group.enumerate(threads, recurse);
    +        } while (count >= threads.length);
    +
    +        final List<Thread> result = new ArrayList<Thread>(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<ThreadGroup> findThreadGroups(final ThreadGroup group,
final boolean recurse, final ThreadGroupPredicate predicate){
    +        if (group == null) {
    +            throw new IllegalArgumentException("The group must not be null");
    +        }
    +        if (predicate == null) {
    +            throw new IllegalArgumentException("The predicate must not be null");
    +        }
    +        
    +        int count = group.activeGroupCount();
    +        ThreadGroup[] threadGroups;
    +        do {
    +            threadGroups = new ThreadGroup[count + (count>>1) + 1];
    --- End diff --
    
    ok, maybe add a comment, so that a maintainer in 3 years will not say WTF? :)


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