Github user peteryhwong commented on a diff in the pull request:
https://github.com/apache/commons-lang/pull/78#discussion_r29562502
--- Diff: src/main/java/org/apache/commons/lang3/ThreadUtils.java ---
@@ -0,0 +1,459 @@
+/*
+ * 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>();
+ for(final ThreadGroup group : findThreadGroups(new
NamePredicate(threadGroupName))) {
+ result.addAll(findThreads(group, false, new
NamePredicate(threadName)));
+ }
+ 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.iterator().hasNext()) {
+ 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");
+ }
+
+ final List<Thread> result = new ArrayList<Thread>();
--- End diff --
If result is defined after the do while loop, it can be initialised with
count as the initial capacity, thereby avoid the potential additional array
allocation/copy when invoking add().
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