commons-net.jar is the bytecode of Apache Commons Net library, which implements the client side of many basic Internet protocols.

Apache Commons Net Source Code files are provided in the binary packge (commons-net-3.8.0-bin.zip). You can download it at Apache Commons Net Website.

The source code of commons-net-3.8.0.jar is provided below:

⏎ org/apache/commons/net/nntp/Threader.java

/*
 * 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.net.nntp;

/**
 * This is an implementation of a message threading algorithm, as originally devised by Zamie Zawinski.
 * See <a href="http://www.jwz.org/doc/threading.html">http://www.jwz.org/doc/threading.html</a> for details.
 * For his Java implementation, see
 * <a href="http://lxr.mozilla.org/mozilla/source/grendel/sources/grendel/view/Threader.java">
 * http://lxr.mozilla.org/mozilla/source/grendel/sources/grendel/view/Threader.java</a>
 */

import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Threader {

    /**
     * The client passes in a list of Threadable objects, and
     * the Threader constructs a connected 'graph' of messages
     * @param messages list of messages to thread, must not be empty
     * @return null if messages == null or root.child == null or messages list is empty
     * @since 2.2
     */
    public Threadable thread(final List<? extends Threadable> messages) {
        return thread((Iterable<? extends Threadable>)messages);
    }

    /**
     * The client passes in a list of Iterable objects, and
     * the Threader constructs a connected 'graph' of messages
     * @param messages iterable of messages to thread, must not be empty
     * @return null if messages == null or root.child == null or messages list is empty
     * @since 3.0
     */
    public Threadable thread(final Iterable<? extends Threadable> messages) {
        if (messages == null) {
            return null;
        }

        HashMap<String,ThreadContainer> idTable = new HashMap<>();

        // walk through each Threadable element
        for (final Threadable t : messages) {
            if (!t.isDummy()) {
                buildContainer(t, idTable);
            }
        }

        if (idTable.isEmpty()) {
            return null;
        }

        final ThreadContainer root = findRootSet(idTable);
        idTable.clear();
        idTable = null;

        pruneEmptyContainers(root);

        root.reverseChildren();
        gatherSubjects(root);

        if (root.next != null) {
            throw new RuntimeException("root node has a next:" + root);
        }

        for (ThreadContainer r = root.child; r != null; r = r.next) {
            if (r.threadable == null) {
                r.threadable = r.child.threadable.makeDummy();
            }
        }

        final Threadable result = (root.child == null ? null : root.child.threadable);
        root.flush();

        return result;
    }

    /**
     *
     * @param threadable
     * @param idTable
     */
    private void buildContainer(final Threadable threadable, final HashMap<String,ThreadContainer> idTable) {
        String id = threadable.messageThreadId();
        ThreadContainer container = idTable.get(id);
        int bogusIdCount = 0;

        // A ThreadContainer exists for this id already. This should be a forward reference, but may
        // be a duplicate id, in which case we will need to generate a bogus placeholder id
        if (container != null) {
            if (container.threadable != null) { // oops! duplicate ids...
                bogusIdCount++ ; // Avoid dead local store warning
                id = "<Bogus-id:" + (bogusIdCount) + ">";
                container = null;
            } else {
                // The container just contained a forward reference to this message, so let's
                // fill in the threadable field of the container with this message
                container.threadable = threadable;
            }
        }

        // No container exists for that message Id. Create one and insert it into the hash table.
        if (container == null) {
            container = new ThreadContainer();
            container.threadable = threadable;
            idTable.put(id, container);
        }

        // Iterate through all of the references and create ThreadContainers for any references that
        // don't have them.
        ThreadContainer parentRef = null;
        {
            final String[] references = threadable.messageThreadReferences();
            for (final String refString : references)
            {
                ThreadContainer ref = idTable.get(refString);

                // if this id doesnt have a container, create one
                if (ref == null) {
                    ref = new ThreadContainer();
                    idTable.put(refString, ref);
                }

                // Link references together in the order they appear in the References: header,
                // IF they dont have a have a parent already &&
                // IF it will not cause a circular reference
                if ((parentRef != null)
                    && (ref.parent == null)
                    && (parentRef != ref)
                    && !(ref.findChild(parentRef))) {
                    // Link ref into the parent's child list
                    ref.parent = parentRef;
                    ref.next = parentRef.child;
                    parentRef.child = ref;
                }
                parentRef = ref;
            }
        }

        // parentRef is now set to the container of the last element in the references field. make that
        // be the parent of this container, unless doing so causes a circular reference
        if (parentRef != null
            && (parentRef == container || container.findChild(parentRef)))
        {
            parentRef = null;
        }

        // if it has a parent already, its because we saw this message in a References: field, and presumed
        // a parent based on the other entries in that field. Now that we have the actual message, we can
        // throw away the old parent and use this new one
        if (container.parent != null) {
            ThreadContainer rest, prev;

            for (prev = null, rest = container.parent.child;
                rest != null;
                prev = rest, rest = rest.next) {
                if (rest == container) {
                    break;
                }
            }

            if (rest == null) {
                throw new RuntimeException(
                    "Didnt find "
                        + container
                        + " in parent"
                        + container.parent);
            }

            // Unlink this container from the parent's child list
            if (prev == null) {
                container.parent.child = container.next;
            } else {
                prev.next = container.next;
            }

            container.next = null;
            container.parent = null;
        }

        // If we have a parent, link container into the parents child list
        if (parentRef != null) {
            container.parent = parentRef;
            container.next = parentRef.child;
            parentRef.child = container;
        }
    }

    /**
     * Find the root set of all existing ThreadContainers
     * @param idTable
     * @return root the ThreadContainer representing the root node
     */
    private ThreadContainer findRootSet(final HashMap<String, ThreadContainer> idTable) {
        final ThreadContainer root = new ThreadContainer();
        final Iterator<Map.Entry<String, ThreadContainer>> iter = idTable.entrySet().iterator();

        while (iter.hasNext()) {
            final Map.Entry<String, ThreadContainer> entry = iter.next();
            final ThreadContainer c = entry.getValue();
            if (c.parent == null) {
                if (c.next != null) {
                    throw new RuntimeException(
                            "c.next is " + c.next.toString());
                }
                c.next = root.child;
                root.child = c;
            }
        }
        return root;
    }

    /**
     * Delete any empty or dummy ThreadContainers
     * @param parent
     */
    private void pruneEmptyContainers(final ThreadContainer parent) {
        ThreadContainer container, prev, next;
        for (prev = null, container = parent.child, next = container.next;
            container != null;
            prev = container,
                container = next,
                next = (container == null ? null : container.next)) {

            // Is it empty and without any children? If so,delete it
            if (container.threadable == null && container.child == null) {
                if (prev == null) {
                    parent.child = container.next;
                } else {
                    prev.next = container.next;
                }

                // Set container to prev so that prev keeps its same value the next time through the loop
                container = prev;
            }

            // Else if empty, with kids, and (not at root or only one kid)
            else if (
                container.threadable == null
                    && container.child != null
                    && (container.parent != null
                        || container.child.next == null)) {
                // We have an invalid/expired message with kids. Promote the kids to this level.
                ThreadContainer tail;
                final ThreadContainer kids = container.child;

                // Remove this container and replace with 'kids'.
                if (prev == null) {
                    parent.child = kids;
                } else {
                    prev.next = kids;
                }

                // Make each child's parent be this level's parent -> i.e. promote the children.
                // Make the last child's next point to this container's next
                // i.e. splice kids into the list in place of container
                for (tail = kids; tail.next != null; tail = tail.next) {
                    tail.parent = container.parent;
                }

                tail.parent = container.parent;
                tail.next = container.next;

                // next currently points to the item after the inserted items in the chain - reset that so we process the newly
                // promoted items next time round
                next = kids;

                // Set container to prev so that prev keeps its same value the next time through the loop
                container = prev;
            } else if (container.child != null) {
                // A real message , with kids
                // Iterate over the children
                pruneEmptyContainers(container);
            }
        }
    }

    /**
     *  If any two members of the root set have the same subject, merge them.
     *  This is to attempt to accomodate messages without References: headers.
     * @param root
     */
    private void gatherSubjects(final ThreadContainer root) {

        int count = 0;

        for (ThreadContainer c = root.child; c != null; c = c.next) {
            count++;
        }

        // TODO verify this will avoid rehashing
        HashMap<String, ThreadContainer> subjectTable = new HashMap<>((int) (count * 1.2), (float) 0.9);
        count = 0;

        for (ThreadContainer c = root.child; c != null; c = c.next) {
            Threadable threadable = c.threadable;

            // No threadable? If so, it is a dummy node in the root set.
            // Only root set members may be dummies, and they alway have at least 2 kids
            // Take the first kid as representative of the subject
            if (threadable == null) {
                threadable = c.child.threadable;
            }

            final String subj = threadable.simplifiedSubject();

            if (subj == null || subj.isEmpty()) {
                continue;
            }

            final ThreadContainer old = subjectTable.get(subj);

            // Add this container to the table iff:
            // - There exists no container with this subject
            // - or this is a dummy container and the old one is not - the dummy one is
            // more interesting as a root, so put it in the table instead
            // - The container in the table has a "Re:" version of this subject, and
            // this container has a non-"Re:" version of this subject. The non-"Re:" version
            // is the more interesting of the two.
            if (old == null
                || (c.threadable == null && old.threadable != null)
                || (old.threadable != null
                    && old.threadable.subjectIsReply()
                    && c.threadable != null
                    && !c.threadable.subjectIsReply())) {
                subjectTable.put(subj, c);
                count++;
            }
        }

        // If the table is empty, we're done
        if (count == 0) {
            return;
        }

        // subjectTable is now populated with one entry for each subject which occurs in the
        // root set. Iterate over the root set, and gather together the difference.
        ThreadContainer prev, c, rest;
        for (prev = null, c = root.child, rest = c.next;
            c != null;
            prev = c, c = rest, rest = (rest == null ? null : rest.next)) {
            Threadable threadable = c.threadable;

            // is it a dummy node?
            if (threadable == null) {
                threadable = c.child.threadable;
            }

            final String subj = threadable.simplifiedSubject();

            // Dont thread together all subjectless messages
            if (subj == null || subj.isEmpty()) {
                continue;
            }

            final ThreadContainer old = subjectTable.get(subj);

            if (old == c) { // That's us
                continue;
            }

            // We have now found another container in the root set with the same subject
            // Remove the "second" message from the root set
            if (prev == null) {
                root.child = c.next;
            } else {
                prev.next = c.next;
            }
            c.next = null;

            if (old.threadable == null && c.threadable == null) {
                // both dummies - merge them
                ThreadContainer tail;
                for (tail = old.child;
                    tail != null && tail.next != null;
                    tail = tail.next) {
                    // do nothing
                }

                if (tail != null) { // protect against possible NPE
                    tail.next = c.child;
                }

                for (tail = c.child; tail != null; tail = tail.next) {
                    tail.parent = old;
                }

                c.child = null;
            } else if (
                old.threadable == null
                    || (c.threadable != null
                        && c.threadable.subjectIsReply()
                        && !old.threadable.subjectIsReply())) {
                // Else if old is empty, or c has "Re:" and old does not  ==> make this message a child of old
                c.parent = old;
                c.next = old.child;
                old.child = c;
            } else {
                // else make the old and new messages be children of a new dummy container.
                // We create a new container object for old.msg and empty the old container
                final ThreadContainer newc = new ThreadContainer();
                newc.threadable = old.threadable;
                newc.child = old.child;

                for (ThreadContainer tail = newc.child;
                    tail != null;
                    tail = tail.next)
                {
                    tail.parent = newc;
                }

                old.threadable = null;
                old.child = null;

                c.parent = old;
                newc.parent = old;

                // Old is now a dummy- give it 2 kids , c and newc
                old.child = c;
                c.next = newc;
            }
            // We've done a merge, so keep the same prev
            c = prev;
        }

        subjectTable.clear();
        subjectTable = null;

    }


    // DEPRECATED METHODS - for API compatibility only - DO NOT USE

    /**
     * The client passes in an array of Threadable objects, and
     * the Threader constructs a connected 'graph' of messages
     * @param messages array of messages to thread, must not be empty
     * @return null if messages == null or root.child == null or messages array is empty
     * @deprecated (2.2) prefer {@link #thread(List)}
     */
    @Deprecated
    public Threadable thread(final Threadable[] messages) {
        if (messages == null) {
            return null;
        }
        return thread(Arrays.asList(messages));
    }

}

⏎ org/apache/commons/net/nntp/Threader.java

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File name: commons-net-3.8.0-sources.jar
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Release date: 2020-01-22
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