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 Bagprivate Map _map = null;/ 底層數(shù)據(jù)存儲區(qū)private i

3、nt _total = 0; / 元素總個數(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(object,

4、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+;_map.clear(

5、);_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() Object current

6、 = 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() != size() return false;for

7、 (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 iterator() return new BagIterator

8、(this, extractList().iterator();原始迭代器static class BagIterator implements Iterator 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, Iteratorsupport) _parent = parent;_support = su

9、pport;_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 (_parent.modCount() != _mods) throw

10、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(object);if (nCopies nCopies) _ma

11、p.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 removeAll(Collection coll) boolean result = false;if (coll != null) Iterator i = coll.iterator(

12、);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 other) boolean result = false;Bag excess = new HashBag();Iterator i = uniqueSet().iterator();wh

13、ile (i.hasNext() Object current = i.next();int myCount = getCount(current);int otherCount = other.getCount(current);if (1 = otherCount & otherCount 0; index-) result.add(current);return result;private int modCount() return _mods;public String toString() StringBuffer buf = new StringBuffer();buf.appe

14、nd();Iterator i = uniqueSet().iterator();while (i.hasNext() Object current = 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 Has

15、hBag() super(new HashMap();public HashBag(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);p

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

17、UnmodifiableBag.decorate(new HashBag();/*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，作者應(yīng)該有其他地方要用到吧public static Bag synchronizedBag(Bag bag) return SynchronizedBag.decorat

18、e(bag);public static Bag unmodifiableBag(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 tra

19、nsformedBag(Bag bag,Transformer transformer) return TransformedBag.decorate(bag, transformer);public static SortedBagsynchronizedSortedBag(SortedBag bag) return SynchronizedSortedBag.decorate(bag);public static SortedBagunmodifiableSortedBag(SortedBag bag) return UnmodifiableSortedBag.decorate(bag);public static SortedBagpredicatedSortedBag(SortedBag bag, Predicate predicate) return PredicatedSortedBag.decorate(bag, predicate);public static SortedBag typedSortedBag(SortedBagbag, Class