org.apache.commons.collections.bag.AbstractMapBag Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections.bag;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.apache.commons.collections.Bag;
import org.apache.commons.collections.set.UnmodifiableSet;
/**
* Abstract implementation of the {@link Bag} interface to simplify the creation
* of subclass implementations.
*
* Subclasses specify a Map implementation to use as the internal storage.
* 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 Commons Collections 3.0 (previously DefaultMapBag v2.0)
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Chuck Burdick
* @author Michael A. Smith
* @author Stephen Colebourne
* @author Janek Bogucki
* @author Steve Clark
*/
public abstract class AbstractMapBag implements Bag {
/** The map to use to store the data */
private transient Map map;
/** The current total size of the bag */
private int size;
/** The modification count for fail fast iterators */
private transient int modCount;
/** The modification count for fail fast iterators */
private transient Set uniqueSet;
/**
* Constructor needed for subclass serialisation.
*
*/
protected AbstractMapBag() {
super();
}
/**
* Constructor that assigns the specified Map as the backing store.
* The map must be empty and non-null.
*
* @param map the map to assign
*/
protected AbstractMapBag(Map map) {
super();
this.map = map;
}
/**
* Utility method for implementations to access the map that backs
* this bag. Not intended for interactive use outside of subclasses.
*
* @return the map being used by the Bag
*/
protected Map getMap() {
return map;
}
//-----------------------------------------------------------------------
/**
* Returns the number of elements in this bag.
*
* @return current size of the bag
*/
public int size() {
return size;
}
/**
* Returns true if the underlying map is empty.
*
* @return true if bag is empty
*/
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Returns the number of occurrence of the given element in this bag
* by looking up its count in the underlying map.
*
* @param object the object to search for
* @return the number of occurrences of the object, zero if not found
*/
public int getCount(Object object) {
MutableInteger count = (MutableInteger) map.get(object);
if (count != null) {
return count.value;
}
return 0;
}
//-----------------------------------------------------------------------
/**
* Determines if the bag contains the given element by checking if the
* underlying map contains the element as a key.
*
* @param object the object to search for
* @return true if the bag contains the given element
*/
public boolean contains(Object object) {
return map.containsKey(object);
}
/**
* Determines if the bag contains the given elements.
*
* @param coll the collection to check against
* @return true if the Bag contains all the collection
*/
public boolean containsAll(Collection coll) {
if (coll instanceof Bag) {
return containsAll((Bag) coll);
}
return containsAll(new HashBag(coll));
}
/**
* Returns true if the bag contains all elements in
* the given collection, respecting cardinality.
*
* @param other the bag to check against
* @return true if the Bag contains all the collection
*/
boolean containsAll(Bag other) {
boolean result = true;
Iterator it = other.uniqueSet().iterator();
while (it.hasNext()) {
Object current = it.next();
boolean contains = getCount(current) >= other.getCount(current);
result = result && contains;
}
return result;
}
//-----------------------------------------------------------------------
/**
* Gets an iterator over the bag elements.
* Elements present in the Bag more than once will be returned repeatedly.
*
* @return the iterator
*/
public Iterator iterator() {
return new BagIterator(this);
}
/**
* Inner class iterator for the Bag.
*/
static class BagIterator implements Iterator {
private AbstractMapBag parent;
private Iterator entryIterator;
private Map.Entry current;
private int itemCount;
private final int mods;
private boolean canRemove;
/**
* Constructor.
*
* @param parent the parent bag
*/
public BagIterator(AbstractMapBag parent) {
this.parent = parent;
this.entryIterator = parent.map.entrySet().iterator();
this.current = null;
this.mods = parent.modCount;
this.canRemove = false;
}
public boolean hasNext() {
return (itemCount > 0 || entryIterator.hasNext());
}
public Object next() {
if (parent.modCount != mods) {
throw new ConcurrentModificationException();
}
if (itemCount == 0) {
current = (Map.Entry) entryIterator.next();
itemCount = ((MutableInteger) current.getValue()).value;
}
canRemove = true;
itemCount--;
return current.getKey();
}
public void remove() {
if (parent.modCount != mods) {
throw new ConcurrentModificationException();
}
if (canRemove == false) {
throw new IllegalStateException();
}
MutableInteger mut = (MutableInteger) current.getValue();
if (mut.value > 1) {
mut.value--;
} else {
entryIterator.remove();
}
parent.size--;
canRemove = false;
}
}
//-----------------------------------------------------------------------
/**
* Adds a new element to the bag, incrementing its count in the underlying map.
*
* @param object the object to add
* @return true if the object was not already in the uniqueSet
*/
public boolean add(Object object) {
return add(object, 1);
}
/**
* Adds a new element to the bag, incrementing its count in the map.
*
* @param object the object to search for
* @param nCopies the number of copies to add
* @return true if the object was not already in the uniqueSet
*/
public boolean add(Object object, int nCopies) {
modCount++;
if (nCopies > 0) {
MutableInteger mut = (MutableInteger) map.get(object);
size += nCopies;
if (mut == null) {
map.put(object, new MutableInteger(nCopies));
return true;
} else {
mut.value += nCopies;
return false;
}
} else {
return false;
}
}
/**
* Invokes {@link #add(Object)} for each element in the given collection.
*
* @param coll the collection to add
* @return true if this call changed the bag
*/
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;
}
//-----------------------------------------------------------------------
/**
* Clears the bag by clearing the underlying map.
*/
public void clear() {
modCount++;
map.clear();
size = 0;
}
/**
* Removes all copies of the specified object from the bag.
*
* @param object the object to remove
* @return true if the bag changed
*/
public boolean remove(Object object) {
MutableInteger mut = (MutableInteger) map.get(object);
if (mut == null) {
return false;
}
modCount++;
map.remove(object);
size -= mut.value;
return true;
}
/**
* Removes a specified number of copies of an object from the bag.
*
* @param object the object to remove
* @param nCopies the number of copies to remove
* @return true if the bag changed
*/
public boolean remove(Object object, int nCopies) {
MutableInteger mut = (MutableInteger) map.get(object);
if (mut == null) {
return false;
}
if (nCopies <= 0) {
return false;
}
modCount++;
if (nCopies < mut.value) {
mut.value -= nCopies;
size -= nCopies;
} else {
map.remove(object);
size -= mut.value;
}
return true;
}
/**
* Removes objects from the bag according to their count in the specified collection.
*
* @param coll the collection to use
* @return true if the bag changed
*/
public boolean removeAll(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;
}
/**
* Remove any members of the bag that are not in the given
* bag, respecting cardinality.
*
* @param coll the collection to retain
* @return true if this call changed the collection
*/
public boolean retainAll(Collection coll) {
if (coll instanceof Bag) {
return retainAll((Bag) coll);
}
return retainAll(new HashBag(coll));
}
/**
* Remove any members of the bag that are not in the given
* bag, respecting cardinality.
* @see #retainAll(Collection)
*
* @param other the bag to retain
* @return true if this call changed the collection
*/
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;
}
//-----------------------------------------------------------------------
/**
* Mutable integer class for storing the data.
*/
protected static class MutableInteger {
/** The value of this mutable. */
protected int value;
/**
* Constructor.
* @param value the initial value
*/
MutableInteger(int value) {
this.value = value;
}
public boolean equals(Object obj) {
if (obj instanceof MutableInteger == false) {
return false;
}
return ((MutableInteger) obj).value == value;
}
public int hashCode() {
return value;
}
}
//-----------------------------------------------------------------------
/**
* Returns an array of all of this bag's elements.
*
* @return an array of all of this bag's elements
*/
public Object[] toArray() {
Object[] result = new Object[size()];
int i = 0;
Iterator it = map.keySet().iterator();
while (it.hasNext()) {
Object current = it.next();
for (int index = getCount(current); index > 0; index--) {
result[i++] = current;
}
}
return result;
}
/**
* Returns an array of all of this bag's elements.
*
* @param array the array to populate
* @return an array of all of this bag's elements
*/
public Object[] toArray(Object[] array) {
int size = size();
if (array.length < size) {
array = (Object[]) Array.newInstance(array.getClass().getComponentType(), size);
}
int i = 0;
Iterator it = map.keySet().iterator();
while (it.hasNext()) {
Object current = it.next();
for (int index = getCount(current); index > 0; index--) {
array[i++] = current;
}
}
if (array.length > size) {
array[size] = null;
}
return array;
}
/**
* Returns an unmodifiable view of the underlying map's key set.
*
* @return the set of unique elements in this bag
*/
public Set uniqueSet() {
if (uniqueSet == null) {
uniqueSet = UnmodifiableSet.decorate(map.keySet());
}
return uniqueSet;
}
//-----------------------------------------------------------------------
/**
* Write the map out using a custom routine.
* @param out the output stream
* @throws IOException
*/
protected void doWriteObject(ObjectOutputStream out) throws IOException {
out.writeInt(map.size());
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
out.writeObject(entry.getKey());
out.writeInt(((MutableInteger) entry.getValue()).value);
}
}
/**
* Read the map in using a custom routine.
* @param map the map to use
* @param in the input stream
* @throws IOException
* @throws ClassNotFoundException
*/
protected void doReadObject(Map map, ObjectInputStream in) throws IOException, ClassNotFoundException {
this.map = map;
int entrySize = in.readInt();
for (int i = 0; i < entrySize; i++) {
Object obj = in.readObject();
int count = in.readInt();
map.put(obj, new MutableInteger(count));
size += count;
}
}
//-----------------------------------------------------------------------
/**
* Compares this Bag to another.
* This Bag equals another Bag if it contains the same number of occurrences of
* the same elements.
*
* @param object the Bag to compare to
* @return true if equal
*/
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 (Iterator it = map.keySet().iterator(); it.hasNext();) {
Object element = it.next();
if (other.getCount(element) != getCount(element)) {
return false;
}
}
return true;
}
/**
* Gets a hash code for the Bag compatible with the definition of equals.
* The hash code is defined as the sum total of a hash code for each element.
* The per element hash code is defined as
* (e==null ? 0 : e.hashCode()) ^ noOccurances).
* This hash code is compatible with the Set interface.
*
* @return the hash code of the Bag
*/
public int hashCode() {
int total = 0;
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Object element = entry.getKey();
MutableInteger count = (MutableInteger) entry.getValue();
total += (element == null ? 0 : element.hashCode()) ^ count.value;
}
return total;
}
/**
* Implement a toString() method suitable for debugging.
*
* @return a debugging toString
*/
public String toString() {
if (size() == 0) {
return "[]";
}
StringBuffer buf = new StringBuffer();
buf.append('[');
Iterator it = uniqueSet().iterator();
while (it.hasNext()) {
Object current = it.next();
int count = getCount(current);
buf.append(count);
buf.append(':');
buf.append(current);
if (it.hasNext()) {
buf.append(',');
}
}
buf.append(']');
return buf.toString();
}
}