Java教程CommonsCollections學(xué)習(xí)筆記(一)

1、Java 教程 :CommonsCollections 學(xué)習(xí)筆記(一)public interface Bag extends Collectionint getCount(Object object);boolean add(Object object);boolean add(Object object, int nCopies);boolean remove(Object object);boolean remove(Object object, int nCopies);Set uniqueSet();int size();boolean containsAll(Collection

2、coll); boolean removeAll(Collection coll);boolean retainAll(Collection coll);Iterator iterator();public interface SortedBag extends Bagpublic Comparator comparator();public Object first();public Object last();public abstract class DefaultMapBag implements Bag private Map _map = null;/ 底層數(shù)據(jù)存儲(chǔ)區(qū)private

3、 int _total = 0; / 元素總個(gè)數(shù)private int _mods = 0;/ 修改次數(shù) public DefaultMapBag() protected DefaultMapBag(Map map) setMap(map);public boolean add(Object object) return add(object, 1);public boolean add(Object object, int nCopies) _mods+;if (nCopies > 0) int count = (nCopies + getCount(object); _map.put

4、(object, new Integer(count);_total += nCopies;return (count = nCopies); else return false;public boolean addAll(Collection coll) boolean changed = false;Iterator i = coll.iterator(); while (i.hasNext() boolean added = add(i.next(); changed = changed | added; return changed; public void clear() _mods

5、+;_map.clear();_total = 0;public boolean contains(Object object) return _map.containsKey(object);public boolean containsAll(Collection coll) return containsAll(new HashBag(coll);public boolean containsAll(Bag other) boolean result = true;Iterator i = other.uniqueSet().iterator(); while (i.hasNext()

6、Object current = i.next();boolean contains = getCount(current) >= other.getCount(current);result = result && contains;return result;public boolean equals(Object object) if (object = this) return true;if (object instanceof Bag = false) return false;Bag other = (Bag) object;if (other.size()

7、 != size() return false;for (Iterator it = _map.keySet().iterator(); it.hasNext();) Object element = it.next();if (other.getCount(element) != getCount(element) return false;return true;public int hashCode() return _map.hashCode();public boolean isEmpty() return _map.isEmpty(); public Iterator iterat

8、or() return new BagIterator(this, extractList().iterator();static class BagIterator implements Iterator 原始迭代器private DefaultMapBag _parent = null;private Iterator _support = null;/ private Object _current = null;/ 當(dāng)前元素 private int _mods = 0;public BagIterator(DefaultMapBag parent, Iterator support)

9、_parent = parent;_support = support;_current = null;_mods = parent.modCount();public boolean hasNext() return _support.hasNext();public Object next() if (_parent.modCount() != _mods) throw new ConcurrentModificationException();_current = _support.next();return _current;public void remove() if (_pare

10、nt.modCount() != _mods) throw new ConcurrentModificationException();_support.remove();_parent.remove(_current, 1);_mods+;public boolean remove(Object object) return remove(object, getCount(object);public boolean remove(Object object, int nCopies) _mods+;boolean result = false;int count = getCount(ob

11、ject);if (nCopies <= 0) result = false; else if (count > nCopies) _map.put(object, new Integer(count - nCopies);result = true;_total -= nCopies; else / count > 0 && count <= i/ need toremove allresult = (_map.remove(object) != null);_total -= count; return result;public boolean r

12、emoveAll(Collection coll) boolean result = false;if (coll != null) Iterator i = coll.iterator();while (i.hasNext() boolean changed = remove(i.next(), 1); result = result | changed; return result;public boolean retainAll(Collection coll) return retainAll(new HashBag(coll);public boolean retainAll(Bag

13、 other) boolean result = false;Bag excess = new HashBag();Iterator i = uniqueSet().iterator();while (i.hasNext() Object current = i.next();int myCount = getCount(current);int otherCount = other.getCount(current);if (1 <= otherCount && otherCount <= myCount) excess.add(current, myCount

14、- otherCount); else excess.add(current, myCount);if (!excess.isEmpty() result = removeAll(excess);return result;public Object toArray() return extractList().toArray();public Object toArray(Object array) return extractList().toArray(array);public int getCount(Object object) int result = 0;Integer cou

15、nt = MapUtils.getInteger(_map, object); if (count != null) result = Value();return result;public Set uniqueSet() return UnmodifiableSet.decorate(_map.keySet();public int size() return _total;protected int calcTotalSize() _total = extractList().size();return _total;protected void setMap(Map

16、map) if (map = null | map.isEmpty() = false) throw new IllegalArgumentException("The map must be non-null and empty");_map = map;protected Map getMap() return _map;private List extractList() List result = new ArrayList();Iterator i = uniqueSet().iterator();while (i.hasNext() Object current

17、 = i.next();for (int index = getCount(current); index > 0; index-) result.add(current);return result;private int modCount() return _mods;public String toString() StringBuffer buf = new StringBuffer(); buf.append("");Iterator i = uniqueSet().iterator();while (i.hasNext() Object current =

18、 i.next();int count = getCount(current);buf.append(count);buf.append(":");buf.append(current);if (i.hasNext() buf.append(",");buf.append("");return buf.toString();public class HashBag extends DefaultMapBag implements Bagpublic HashBag() super(new HashMap();public HashBa

19、g(Collection coll) this();addAll(coll);public class TreeBag extends DefaultMapBag implements SortedBagpublic TreeBag() super(new TreeMap();public TreeBag(Comparator comparator) super(new TreeMap(comparator);public TreeBag(Collection coll) this();addAll(coll);public Object first() return (SortedMap)

20、getMap().firstKey();public Object last() return (SortedMap) getMap().lastKey();public Comparator comparator() return (SortedMap) getMap() parator();使用 decorate 模式的 Bag 工具類 public class BagUtils/* * An empty unmodifiable bag.*/public static final Bag EMPTY_BAG =UnmodifiableBag.decorate(new HashBag();

21、/* An empty unmodifiable sorted bag.*/public static final Bag EMPTY_SORTED_BAG =UnmodifiableSortedBag.decorate(new TreeBag();public BagUtils() / 這里按常理不應(yīng)該是 public ，應(yīng)該是 private 才對(duì)，作者應(yīng)該有其他地方要用到吧public static Bag synchronizedBag(Bag bag) return SynchronizedBag.decorate(bag);public static Bag unmodifiabl

22、eBag(Bag bag) return UnmodifiableBag.decorate(bag);public static Bag predicatedBag(Bag bag, Predicate predicate) return PredicatedBag.decorate(bag, predicate);public static Bag typedBag(Bag bag, Class type) return TypedBag.decorate(bag, type);public static Bag transformedBag(Bag bag, Transformer tra

23、nsformer) return TransformedBag.decorate(bag, transformer); public static SortedBag synchronizedSortedBag(SortedBag bag) return SynchronizedSortedBag.decorate(bag);public static SortedBag unmodifiableSortedBag(SortedBag bag) return UnmodifiableSortedBag.decorate(bag);public static SortedBagpredicatedSortedBag(SortedBag bag, Predicate predic