* * The map will be used to map bag elements to a number; the number represents * the number of occurrences of that element in the bag.
*
* @since 2.0
* @author Chuck Burdick
* @author Michael A. Smith
**/
public abstract class DefaultMapBag implements Bag {
private Map _map = null;
private int _total = 0;
private int _mods = 0;
/**
* Constructor. Subclasses should invoke {@link #setMap(Map)} in
* their constructors.
*/
public DefaultMapBag() {
}
/**
* Adds a new element to the bag by incrementing its count in the
* underlying map.
*
* @see Bag#add(Object)
*/
public boolean add(Object o) {
return add(o, 1);
}
/**
* Adds a new element to the bag by incrementing its count in the map.
*
* @see Bag#add(Object, int)
*/
public boolean add(Object o, int i) {
_mods++;
if (i > 0) {
int count = (i + getCount(o));
_map.put(o, new Integer(count));
_total += i;
return (count == i);
} else {
return false;
}
}
/**
* Invokes {@link #add(Object)} for each element in the given collection.
*
* @see Bag#addAll(Collection)
*/
public boolean addAll(Collection c) {
boolean changed = false;
Iterator i = c.iterator();
while (i.hasNext()) {
boolean added = add(i.next());
changed = changed || added;
}
return changed;
}
/**
* Clears the bag by clearing the underlying map.
*/
public void clear() {
_mods++;
_map.clear();
_total = 0;
}
/**
* Determines if the bag contains the given element by checking if the
* underlying map contains the element as a key.
*
* @return true if the bag contains the given element
*/
public boolean contains(Object o) {
return _map.containsKey(o);
}
public boolean containsAll(Collection c) {
return containsAll(new HashBag(c));
}
/**
* Returns true if the bag contains all elements in
* the given collection, respecting cardinality.
* @see #containsAll(Collection)
**/
public boolean containsAll(Bag other) {
boolean result = true;
Iterator i = other.uniqueSet().iterator();
while (i.hasNext()) {
Object current = i.next();
boolean contains =
getCount(current) >= ((Bag)other).getCount(current);
result = result && contains;
}
return result;
}
/**
* Returns true if the given object is not null, has the precise type
* of this bag, and contains the same number of occurrences of all the
* same elements.
*
* @param o the object to test for equality
* @return true if that object equals this bag
*/
public boolean equals(Object o) {
return (o == this ||
(o != null && o.getClass().equals(this.getClass()) &&
((DefaultMapBag)o)._map.equals(this._map)));
}
/**
* Returns the hash code of the underlying map.
*
* @return the hash code of the underlying map
*/
public int hashCode() {
return _map.hashCode();
}
/**
* Returns true if the underlying map is empty.
*
* @return true if there are no elements in this bag
*/
public boolean isEmpty() {
return _map.isEmpty();
}
public Iterator iterator() {
return new BagIterator(this, extractList().iterator());
}
private class BagIterator implements Iterator {
private DefaultMapBag _parent = null;
private Iterator _support = null;
private Object _current = null;
private int _mods = 0;
public BagIterator(DefaultMapBag parent, Iterator support) {
_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 (_parent.modCount() != _mods) {
throw new ConcurrentModificationException();
}
_support.remove();
_parent.remove(_current, 1);
_mods++;
}
}
public boolean remove (Object o) {
return remove(o, getCount(o));
}
public boolean remove (Object o, int i) {
_mods++;
boolean result = false;
int count = getCount(o);
if (i <= 0) {
result = false;
} else if (count > i) {
_map.put(o, new Integer(count - i));
result = true;
_total -= i;
} else { // count > 0 && count <= i
// need to remove all
result = (_map.remove(o) != null);
_total -= count;
}
return result;
}
public boolean removeAll(Collection c) {
boolean result = false;
if (c != null) {
Iterator i = c.iterator();
while (i.hasNext()) {
boolean changed = remove(i.next(), 1);
result = result || changed;
}
}
return result;
}
/**
* Remove any members of the bag that are not in the given
* bag, respecting cardinality.
*
* @return true if this call changed the collection
*/
public boolean retainAll(Collection c) {
return retainAll(new HashBag(c));
}
/**
* Remove any members of the bag that are not in the given
* bag, respecting cardinality.
* @see #retainAll(Collection)
* @return true if this call changed the collection
**/
public boolean retainAll(Bag 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 - otherCount);
} else {
excess.add(current, myCount);
}
}
if (!excess.isEmpty()) {
result = removeAll(excess);
}
return result;
}
/**
* Returns an array of all of this bag's elements.
*
* @return an array of all of this bag's elements
*/
public Object[] toArray() {
return extractList().toArray();
}
/**
* Returns an array of all of this bag's elements.
*
* @param a the array to populate
* @return an array of all of this bag's elements
*/
public Object[] toArray(Object[] a) {
return extractList().toArray(a);
}
/**
* Returns the number of occurrence of the given element in this bag
* by looking up its count in the underlying map.
*
* @see Bag#getCount(Object)
*/
public int getCount(Object o) {
int result = 0;
Integer count = MapUtils.getInteger(_map, o);
if (count != null) {
result = count.intValue();
}
return result;
}
/**
* Returns an unmodifiable view of the underlying map's key set.
*
* @return the set of unique elements in this bag
*/
public Set uniqueSet() {
return Collections.unmodifiableSet(_map.keySet());
}
/**
* Returns the number of elements in this bag.
*
* @return the number of elements in this bag
*/
public int size() {
return _total;
}
/**
* Actually walks the bag to make sure the count is correct and
* resets the running total
**/
protected int calcTotalSize() {
_total = extractList().size();
return _total;
}
/**
* Utility method for implementations to set the map that backs
* this bag. Not intended for interactive use outside of
* subclasses.
**/
protected void setMap(Map m) {
_map = m;
}
/**
* Utility method for implementations to access the map that backs
* this bag. Not intended for interactive use outside of
* subclasses.
**/
protected Map getMap() {
return _map;
}
/**
* Create a list for use in iteration, etc.
**/
private List extractList() {
List result = new ArrayList();
Iterator i = uniqueSet().iterator();
while (i.hasNext()) {
Object current = i.next();
for (int index = getCount(current); index > 0; index--) {
result.add(current);
}
}
return result;
}
/**
* Return number of modifications for iterator
**/
private int modCount() {
return _mods;
}
/**
* Implement a toString() method suitable for debugging
**/
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append("[");
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();
}
}