staticbucketmap.java

JAVA 文章管理系统源码

        synchronized( m_locks[ hash ] )
        {
            Node n = m_buckets[ hash ];
            Node prev = null;

            while( n != null )
            {
                if( n.key == key || ( n.key != null && n.key.equals( key ) ) )
                {
                    // Remove this node from the linked list of nodes.
                    if( null == prev )
                    {
                        // This node was the head, set the next node to be the new head.
                        m_buckets[ hash ] = n.next;
                    }
                    else
                    {
                        // Set the next node of the previous node to be the node after this one.
                        prev.next = n.next;
                    }
                    m_locks[hash].size--;
                    return n.value;
                }

                prev = n;
                n = n.next;
            }
        }

        return null;
    }

    /**
     *  Implements {@link Map#isEmpty()}.
     */
    public final boolean isEmpty()
    {
        return size() == 0;
    }

    /**
     *  Implements {@link Map#clear()}.
     */
    public final void clear()
    {
        for( int i = 0; i < m_buckets.length; i++ )
        {
            Lock lock = m_locks[i];
            synchronized (lock) {
                m_buckets[ i ] = null;
                lock.size = 0;
            }
        }
    }

    /**
     *  Implements {@link Map#equals(Object)}.
     */
    public final boolean equals( Object obj )
    {
        if( obj == null ) return false;
        if( obj == this ) return true;

        if( !( obj instanceof Map ) ) return false;

        Map other = (Map)obj;
        
        return entrySet().equals(other.entrySet());
    }

    /**
     *  Implements {@link Map#hashCode()}.
     */
    public final int hashCode() 
    {
        int hashCode = 0;

        for( int i = 0; i < m_buckets.length; i++ )
        {
            synchronized( m_locks[ i ] )
            {
                Node n = m_buckets[ i ];

                while( n != null )
                {
                    hashCode += n.hashCode();
                    n = n.next;
                }
            }
        }
        return hashCode;
    }

    /**
     * The Map.Entry for the StaticBucketMap.
     */
    private static final class Node implements Map.Entry, KeyValue
    {
        protected Object key;
        protected Object value;
        protected Node next;

        public Object getKey()
        {
            return key;
        }

        public Object getValue()
        {
            return value;
        }

        public int hashCode()
        {
            return ( ( key == null ? 0 : key.hashCode() ) ^
                     ( value == null ? 0 : value.hashCode() ) ); 
        }

        public boolean equals(Object o) {
            if( o == null ) return false;
            if( o == this ) return true;        
            
            if ( ! (o instanceof Map.Entry ) )
                return false;

            Map.Entry e2 = (Map.Entry)o;

            return ((key == null ?
                     e2.getKey() == null : key.equals(e2.getKey())) &&
                    (value == null ?
                     e2.getValue() == null : value.equals(e2.getValue())));
        }

        public Object setValue( Object val )
        {
            Object retVal = value;
            value = val;
            return retVal;
        }
    }

    private final static class Lock {

        public int size;

    }


    private class EntryIterator implements Iterator {

        private ArrayList current = new ArrayList();
        private int bucket;
        private Map.Entry last;


        public boolean hasNext() {
            if (current.size() > 0) return true;
            while (bucket < m_buckets.length) {
                synchronized (m_locks[bucket]) {
                    Node n = m_buckets[bucket];
                    while (n != null) {
                        current.add(n);
                        n = n.next;
                    }
                    bucket++;
                    if (current.size() > 0) return true;
                }
            }
            return false;
        }

        protected Map.Entry nextEntry() {
            if (!hasNext()) throw new NoSuchElementException();
            last = (Map.Entry)current.remove(current.size() - 1);
            return last;
        }

        public Object next() {
            return nextEntry();
        }

        public void remove() {
            if (last == null) throw new IllegalStateException();
            StaticBucketMap.this.remove(last.getKey());
            last = null;
        }

    }

    private class ValueIterator extends EntryIterator {

        public Object next() {
            return nextEntry().getValue();
        }

    }

    private class KeyIterator extends EntryIterator {

        public Object next() {
            return nextEntry().getKey();
        }

    }

    private class EntrySet extends AbstractSet {

        public int size() {
            return StaticBucketMap.this.size();
        }

        public void clear() {
            StaticBucketMap.this.clear();
        }

        public Iterator iterator() {
            return new EntryIterator();
        }

        public boolean contains(Object o) {
            Map.Entry entry = (Map.Entry)o;
            int hash = getHash(entry.getKey());
            synchronized (m_locks[hash]) {
                for (Node n = m_buckets[hash]; n != null; n = n.next) {
                    if (n.equals(entry)) return true;
                }
            }
            return false;
        }

        public boolean remove(Object obj) {
            if (obj instanceof Map.Entry == false) {
                return false;
            }
            Map.Entry entry = (Map.Entry) obj;
            int hash = getHash(entry.getKey());
            synchronized (m_locks[hash]) {
                for (Node n = m_buckets[hash]; n != null; n = n.next) {
                    if (n.equals(entry)) {
                        StaticBucketMap.this.remove(n.getKey());
                        return true;
                    }
                }
            }
            return false;
        }

    }


    private class KeySet extends AbstractSet {

        public int size() {
            return StaticBucketMap.this.size();
        }

        public void clear() {
            StaticBucketMap.this.clear();
        }

        public Iterator iterator() {
            return new KeyIterator();
        }

        public boolean contains(Object o) {
            return StaticBucketMap.this.containsKey(o);
        }

        public boolean remove(Object o) {
            int hash = getHash(o);
            synchronized (m_locks[hash]) {
                for (Node n = m_buckets[hash]; n != null; n = n.next) {
                    Object k = n.getKey();
                    if ((k == o) || ((k != null) && k.equals(o))) {
                        StaticBucketMap.this.remove(k);
                        return true;
                    }
                }
            }
            return false;

        }

    }


    private class Values extends AbstractCollection {

        public int size() {
            return StaticBucketMap.this.size();
        }

        public void clear() {
            StaticBucketMap.this.clear();
        }

        public Iterator iterator() {
            return new ValueIterator();
        }

    }


    /**
     *  Prevents any operations from occurring on this map while the
     *  given {@link Runnable} executes.  This method can be used, for
     *  instance, to execute a bulk operation atomically: 
     *
     *  <pre>
     *    staticBucketMapInstance.atomic(new Runnable() {
     *        public void run() {
     *            staticBucketMapInstance.putAll(map);
     *        }
     *    });
     *  </pre>
     *
     *  It can also be used if you need a reliable iterator:
     *
     *  <pre>
     *    staticBucketMapInstance.atomic(new Runnable() {
     *        public void run() {
     *            Iterator iterator = staticBucketMapInstance.iterator();
     *            while (iterator.hasNext()) {
     *                foo(iterator.next();
     *            }
     *        }
     *    });
     *  </pre>
     *
     *  <B>Implementation note:</B> This method requires a lot of time
     *  and a ton of stack space.  Essentially a recursive algorithm is used
     *  to enter each bucket's monitor.  If you have twenty thousand buckets
     *  in your map, then the recursive method will be invoked twenty thousand
     *  times.  You have been warned.
     *
     *  @param r  the code to execute atomically
     */
    public void atomic(Runnable r) {
        if (r == null) throw new NullPointerException();
        atomic(r, 0);
    }

    private void atomic(Runnable r, int bucket) {
        if (bucket >= m_buckets.length) {
            r.run();
            return;
        }
        synchronized (m_locks[bucket]) {
            atomic(r, bucket + 1);
        }
    }


}