referencemap.java

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    public int size() {
        purge();
        return size;
    }


    /**
     *  Returns <code>true</code> if this map is empty.
     *
     *  @return <code>true</code> if this map is empty
     */
    public boolean isEmpty() {
        purge();
        return size == 0;
    }


    /**
     *  Returns <code>true</code> if this map contains the given key.
     *
     *  @return true if the given key is in this map
     */
    public boolean containsKey(Object key) {
        purge();
        Entry entry = getEntry(key);
        if (entry == null) return false;
        return entry.getValue() != null;
    }


    /**
     *  Returns the value associated with the given key, if any.
     *
     *  @return the value associated with the given key, or <code>null</code>
     *   if the key maps to no value
     */
    public Object get(Object key) {
        purge();
        Entry entry = getEntry(key);
        if (entry == null) return null;
        return entry.getValue();
    }


    /**
     *  Associates the given key with the given value.<p>
     *  Neither the key nor the value may be null.
     *
     *  @param key  the key of the mapping
     *  @param value  the value of the mapping
     *  @return  the last value associated with that key, or 
     *   null if no value was associated with the key
     *  @throws NullPointerException if either the key or value
     *   is null
     */
    public Object put(Object key, Object value) {
        if (key == null) throw new NullPointerException("null keys not allowed");
        if (value == null) throw new NullPointerException("null values not allowed");

        purge();
        if (size + 1 > threshold) resize();

        int hash = key.hashCode();
        int index = indexFor(hash);
        Entry entry = table[index];
        while (entry != null) {
            if ((hash == entry.hash) && key.equals(entry.getKey())) {
                Object result = entry.getValue();
                entry.setValue(value);
                return result;
            }
            entry = entry.next;
        }
        this.size++; 
        modCount++;
        key = toReference(keyType, key, hash);
        value = toReference(valueType, value, hash);
        table[index] = new Entry(key, hash, value, table[index]);
        return null;
    }


    /**
     *  Removes the key and its associated value from this map.
     *
     *  @param key  the key to remove
     *  @return the value associated with that key, or null if
     *   the key was not in the map
     */
    public Object remove(Object key) {
        if (key == null) return null;
        purge();
        int hash = key.hashCode();
        int index = indexFor(hash);
        Entry previous = null;
        Entry entry = table[index];
        while (entry != null) {
            if ((hash == entry.hash) && key.equals(entry.getKey())) {
                if (previous == null) table[index] = entry.next;
                else previous.next = entry.next;
                this.size--;
                modCount++;
                return entry.getValue();
            }
            previous = entry;
            entry = entry.next;
        }
        return null;
    }


    /**
     *  Clears this map.
     */
    public void clear() {
        Arrays.fill(table, null);
        size = 0;
        while (queue.poll() != null); // drain the queue
    }


    /**
     *  Returns a set view of this map's entries.
     *
     *  @return a set view of this map's entries
     */
    public Set entrySet() {
        if (entrySet != null) {
            return entrySet;
        } 
        entrySet = new AbstractSet() {
            public int size() {
                return ReferenceMap.this.size();
            }

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

            public boolean contains(Object o) {
                if (o == null) return false;
                if (!(o instanceof Map.Entry)) return false;
                Map.Entry e = (Map.Entry)o;
                Entry e2 = getEntry(e.getKey());
                return (e2 != null) && e.equals(e2);
            }

            public boolean remove(Object o) {
                boolean r = contains(o);
                if (r) {
                    Map.Entry e = (Map.Entry)o;
                    ReferenceMap.this.remove(e.getKey());
                }
                return r;
            }

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

            public Object[] toArray() {
                return toArray(new Object[0]);
            }

            public Object[] toArray(Object[] arr) {
                ArrayList list = new ArrayList();
                Iterator iterator = iterator();
                while (iterator.hasNext()) {
                    Entry e = (Entry)iterator.next();
                    list.add(new DefaultMapEntry(e.getKey(), e.getValue()));
                }
                return list.toArray(arr);
            }
        };
        return entrySet;
    }


    /**
     *  Returns a set view of this map's keys.
     *
     *  @return a set view of this map's keys
     */
    public Set keySet() {
        if (keySet != null) return keySet;
        keySet = new AbstractSet() {
            public int size() {
                return ReferenceMap.this.size();
            }

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

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


            public boolean remove(Object o) {
                Object r = ReferenceMap.this.remove(o);
                return r != null;
            }

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

            public Object[] toArray() {
                return toArray(new Object[0]);
            }

            public Object[] toArray(Object[] array) {
                Collection c = new ArrayList(size());
                for (Iterator it = iterator(); it.hasNext(); ) {
                    c.add(it.next());
                }
                return c.toArray(array);
            }
        };
        return keySet;
    }


    /**
     *  Returns a collection view of this map's values.
     *
     *  @return a collection view of this map's values.
     */
    public Collection values() {
        if (values != null) return values;
        values = new AbstractCollection()  {
            public int size() {
                return ReferenceMap.this.size();
            }

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

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

            public Object[] toArray() {
                return toArray(new Object[0]);
            }

            public Object[] toArray(Object[] array) {
                Collection c = new ArrayList(size());
                for (Iterator it = iterator(); it.hasNext(); ) {
                    c.add(it.next());
                }
                return c.toArray(array);
            }
        };
        return values;
    }


    // If getKey() or getValue() returns null, it means
    // the mapping is stale and should be removed.
    private class Entry implements Map.Entry, KeyValue {

        Object key;
        Object value;
        int hash;
        Entry next;


        public Entry(Object key, int hash, Object value, Entry next) {
            this.key = key;
            this.hash = hash;
            this.value = value;
            this.next = next;
        }


        public Object getKey() {
            return (keyType > HARD) ? ((Reference)key).get() : key;
        }


        public Object getValue() {
            return (valueType > HARD) ? ((Reference)value).get() : value;
        }


        public Object setValue(Object object) {
            Object old = getValue();
            if (valueType > HARD) ((Reference)value).clear();
            value = toReference(valueType, object, hash);
            return old;
        }


        public boolean equals(Object o) {
            if (o == null) return false;
            if (o == this) return true;
            if (!(o instanceof Map.Entry)) return false;
            
            Map.Entry entry = (Map.Entry)o;
            Object key = entry.getKey();
            Object value = entry.getValue();
            if ((key == null) || (value == null)) return false;
            return key.equals(getKey()) && value.equals(getValue());
        }


        public int hashCode() {
            Object v = getValue();
            return hash ^ ((v == null) ? 0 : v.hashCode());
        }


        public String toString() {
            return getKey() + "=" + getValue();
        }


        boolean purge(Reference ref) {
            boolean r = (keyType > HARD) && (key == ref);
            r = r || ((valueType > HARD) && (value == ref));
            if (r) {
                if (keyType > HARD) ((Reference)key).clear();
                if (valueType > HARD) {
                    ((Reference)value).clear();
                } else if (purgeValues) {
                    value = null;
                }
            }
            return r;
        }
    }


    private class EntryIterator implements Iterator {
        // These fields keep track of where we are in the table.
        int index;
        Entry entry;
        Entry previous;

        // These Object fields provide hard references to the
        // current and next entry; this assures that if hasNext()
        // returns true, next() will actually return a valid element.
        Object nextKey, nextValue;
        Object currentKey, currentValue;

        int expectedModCount;


        public EntryIterator() {
            index = (size() != 0 ? table.length : 0);
            // have to do this here!  size() invocation above
            // may have altered the modCount.
            expectedModCount = modCount;
        }


        public boolean hasNext() {
            checkMod();
            while (nextNull()) {
                Entry e = entry;
                int i = index;
                while ((e == null) && (i > 0)) {
                    i--;
                    e = table[i];
                }
                entry = e;
                index = i;
                if (e == null) {
                    currentKey = null;
                    currentValue = null;
                    return false;
                }
                nextKey = e.getKey();
                nextValue = e.getValue();
                if (nextNull()) entry = entry.next;
            }
            return true;
        }


        private void checkMod() {
            if (modCount != expectedModCount) {
                throw new ConcurrentModificationException();
            }
        }


        private boolean nextNull() {
            return (nextKey == null) || (nextValue == null);
        }

        protected Entry nextEntry() {    
            checkMod();
            if (nextNull() && !hasNext()) throw new NoSuchElementException();
            previous = entry;
            entry = entry.next;
            currentKey = nextKey;
            currentValue = nextValue;
            nextKey = null;
            nextValue = null;
            return previous;
        }


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


        public void remove() {
            checkMod();
            if (previous == null) throw new IllegalStateException();
            ReferenceMap.this.remove(currentKey);
            previous = null;
            currentKey = null;
            currentValue = null;
            expectedModCount = modCount;
        }

    }


    private class ValueIterator extends EntryIterator {
        public Object next() {
            return nextEntry().getValue();
        }
    }


    private class KeyIterator extends EntryIterator {
        public Object next() {
            return nextEntry().getKey();
        }
    }



    // These two classes store the hashCode of the key of
    // of the mapping, so that after they're dequeued a quick
    // lookup of the bucket in the table can occur.


    private static class SoftRef extends SoftReference {
        private int hash;


        public SoftRef(int hash, Object r, ReferenceQueue q) {
            super(r, q);
            this.hash = hash;
        }


        public int hashCode() {
            return hash;
        }
    }


    private static class WeakRef extends WeakReference {
        private int hash;


        public WeakRef(int hash, Object r, ReferenceQueue q) {
            super(r, q);
            this.hash = hash;
        }


        public int hashCode() {
            return hash;
        }
    }


}