A Map that accepts int or Integer keys only
/*
* Copyright 2005 Brian S O'Neill
*
* Licensed 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.
*/
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.io.IOException;
import java.io.Serializable;
/**
* A Map that accepts int or Integer keys only. This class is not thread-safe.
*
* @author Brian S O'Neill
*/
public class IntHashMap<V> extends AbstractMap<Integer, V>
implements Map<Integer, V>, Cloneable, Serializable
{
/**
* The hash table data.
*/
private transient Entry<V> table[];
/**
* The total number of mappings in the hash table.
*/
private transient int count;
/**
* The table is rehashed when its size exceeds this threshold. (The
* value of this field is (int)(capacity * loadFactor).)
*
* @serial
*/
private int threshold;
/**
* The load factor for the hashtable.
*
* @serial
*/
private float loadFactor;
/**
* The number of times this IntHashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the IntHashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of
* the IntHashMap fail-fast. (See ConcurrentModificationException).
*/
private transient int modCount = 0;
/**
* Constructs a new, empty map with the specified initial
* capacity and the specified load factor.
*
* @param initialCapacity the initial capacity of the IntHashMap.
* @param loadFactor the load factor of the IntHashMap
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the load factor is nonpositive.
*/
public IntHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal Initial Capacity: "+
initialCapacity);
}
if (loadFactor <= 0) {
throw new IllegalArgumentException("Illegal Load factor: "+
loadFactor);
}
if (initialCapacity==0) {
initialCapacity = 1;
}
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int)(initialCapacity * loadFactor);
}
/**
* Constructs a new, empty map with the specified initial capacity
* and default load factor, which is <tt>0.75</tt>.
*
* @param initialCapacity the initial capacity of the IntHashMap.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IntHashMap(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
* Constructs a new, empty map with a default capacity and load
* factor, which is <tt>0.75</tt>.
*/
public IntHashMap() {
this(101, 0.75f);
}
/**
* Constructs a new map with the same mappings as the given map. The
* map is created with a capacity of twice the number of mappings in
* the given map or 11 (whichever is greater), and a default load factor,
* which is <tt>0.75</tt>.
*/
public IntHashMap(Map<? extends Integer, ? extends V> t) {
this(Math.max(2 * t.size(), 11), 0.75f);
putAll(t);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map.
*/
public int size() {
return count;
}
/**
* Returns <tt>true</tt> if this map contains no key-value mappings.
*
* @return <tt>true</tt> if this map contains no key-value mappings.
*/
public boolean isEmpty() {
return count == 0;
}
/**
* Returns <tt>true</tt> if this map maps one or more keys to the
* specified value.
*
* @param value value whose presence in this map is to be tested.
* @return <tt>true</tt> if this map maps one or more keys to the
* specified value.
*/
public boolean containsValue(Object value) {
Entry tab[] = table;
if (value == null) {
for (int i = tab.length ; i-- > 0 ;) {
for (Entry e = tab[i] ; e != null ; e = e.next) {
if (e.value == null) {
return true;
}
}
}
} else {
for (int i = tab.length ; i-- > 0 ;) {
for (Entry e = tab[i] ; e != null ; e = e.next) {
if (value.equals(e.value)) {
return true;
}
}
}
}
return false;
}
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
* @param key key whose presence in this Map is to be tested.
*/
public boolean containsKey(Integer key) {
return containsKey(key.intValue());
}
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
* @param key key whose presence in this Map is to be tested.
*/
public boolean containsKey(int key) {
Entry tab[] = table;
int index = (key & 0x7fffffff) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
return true;
}
}
return false;
}
/**
* Returns the value to which this map maps the specified key. Returns
* <tt>null</tt> if the map contains no mapping for this key. A return
* value of <tt>null</tt> does not <i>necessarily</i> indicate that the
* map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to <tt>null</tt>. The <tt>containsKey</tt>
* operation may be used to distinguish these two cases.
*
* @return the value to which this map maps the specified key.
* @param key key whose associated value is to be returned.
*/
public V get(Integer key) {
return get(key.intValue());
}
/**
* Returns the value to which this map maps the specified key. Returns
* <tt>null</tt> if the map contains no mapping for this key. A return
* value of <tt>null</tt> does not <i>necessarily</i> indicate that the
* map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to <tt>null</tt>. The <tt>containsKey</tt>
* operation may be used to distinguish these two cases.
*
* @return the value to which this map maps the specified key.
* @param key key whose associated value is to be returned.
*/
public V get(int key) {
Entry<V> tab[] = table;
int index = (key & 0x7fffffff) % tab.length;
for (Entry<V> e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
return e.value;
}
}
return null;
}
/**
* Rehashes the contents of this map into a new <tt>IntHashMap</tt> instance
* with a larger capacity. This method is called automatically when the
* number of keys in this map exceeds its capacity and load factor.
*/
private void rehash() {
int oldCapacity = table.length;
Entry oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Entry<V> newMap[] = new Entry[newCapacity];
modCount++;
threshold = (int)(newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity ; i-- > 0 ;) {
for (Entry old = oldMap[i] ; old != null ; ) {
Entry e = old;
old = old.next;
int index = (e.key & 0x7fffffff) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the IntHashMap previously associated
* <tt>null</tt> with the specified key.
*/
public V put(Integer key, V value) {
return put(key.intValue(), value);
}
/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for this key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the IntHashMap previously associated
* <tt>null</tt> with the specified key.
*/
public V put(int key, V value) {
// Makes sure the key is not already in the IntHashMap.
Entry<V> tab[] = table;
int index = 0;
index = (key & 0x7fffffff) % tab.length;
for (Entry<V> e = tab[index] ; e != null ; e = e.next) {
if (e.key == key) {
V old = e.value;
e.value = value;
return old;
}
}
modCount++;
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (key & 0x7fffffff) % tab.length;
}
// Creates the new entry.
Entry<V> e = new Entry<V>(key, value, tab[index]);
tab[index] = e;
count++;
return null;
}
/**
* Removes the mapping for this key from this map if present.
*
* @param key key whose mapping is to be removed from the map.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the map previously associated <tt>null</tt>
* with the specified key.
*/
public V remove(Integer key) {
return remove(key.intValue());
}
/**
* Removes the mapping for this key from this map if present.
*
* @param key key whose mapping is to be removed from the map.
* @return previous value associated with specified key, or <tt>null</tt>
* if there was no mapping for key. A <tt>null</tt> return can
* also indicate that the map previously associated <tt>null</tt>
* with the specified key.
*/
public V remove(int key) {
Entry<V> tab[] = table;
int index = (key & 0x7fffffff) % tab.length;
for (Entry<V> e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.key == key) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
V oldValue = e.value;
e.value = null;
return oldValue;
}
}
return null;
}
/**
* Removes all mappings from this map.
*/
public void clear() {
Entry tab[] = table;
modCount++;
for (int index = tab.length; --index >= 0; ) {
tab[index] = null;
}
count = 0;
}
/**
* Returns a shallow copy of this <tt>IntHashMap</tt> instance: the keys and
* values themselves are not cloned.
*
* @return a shallow copy of this map.
*/
public Object clone() {
try {
IntHashMap t = (IntHashMap) super.clone();
t.table = new Entry[table.length];
for (int i = table.length ; i-- > 0 ; ) {
t.table[i] = (table[i] != null) ? (Entry) table[i].clone() : null;
}
t.keySet = null;
t.entrySet = null;
t.values = null;
t.modCount = 0;
return t;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
// Views
private transient Set keySet = null;
private transient Set entrySet = null;
private transient Collection values = null;
/**
* Returns a set view of the keys contained in this map. The set is
* backed by the map, so changes to the map are reflected in the set, and
* vice-versa. The set supports element removal, which removes the
* corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* @return a set view of the keys contained in this map.
*/
public Set<Integer> keySet() {
if (keySet == null) {
keySet = new AbstractSet<Integer>() {
public Iterator iterator() {
return new IntHashIterator(KEYS);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return IntHashMap.this.remove(o) != null;
}
public void clear() {
IntHashMap.this.clear();
}
};
}
return keySet;
}
/**
* Returns a collection view of the values contained in this map. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. The collection supports element
* removal, which removes the corresponding mapping from this map, via the
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a collection view of the values contained in this map.
*/
public Collection<V> values() {
if (values==null) {
values = new AbstractCollection<V>() {
public Iterator iterator() {
return (Iterator) new IntHashIterator(VALUES);
}
public int size() {
return count;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
IntHashMap.this.clear();
}
};
}
return values;
}
/**
* Returns a collection view of the mappings contained in this map. Each
* element in the returned collection is a <tt>Map.Entry</tt>. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. The collection supports element
* removal, which removes the corresponding mapping from the map, via the
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a collection view of the mappings contained in this map.
*/
public Set<Map.Entry<Integer, V>> entrySet() {
if (entrySet==null) {
entrySet = new AbstractSet<Map.Entry<Integer, V>>() {
public Iterator iterator() {
return (Iterator) new IntHashIterator(ENTRIES);
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry entry = (Map.Entry) o;
Integer key = (Integer) entry.getKey();
Entry tab[] = table;
int hash = (key == null ? 0 : key.hashCode());
int index = (hash & 0x7fffffff) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == hash && e.equals(entry)) {
return true;
}
}
return false;
}
public boolean remove(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry entry = (Map.Entry) o;
Integer key = (Integer) entry.getKey();
Entry tab[] = table;
int hash = (key == null ? 0 : key.hashCode());
int index = (hash & 0x7fffffff) % tab.length;
for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.key == hash && e.equals(entry)) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
e.value = null;
return true;
}
}
return false;
}
public int size() {
return count;
}
public void clear() {
IntHashMap.this.clear();
}
};
}
return entrySet;
}
/**
* IntHashMap collision list entry.
*/
private static class Entry<V> implements Map.Entry<Integer, V> {
int key;
V value;
Entry<V> next;
private Integer objectKey;
Entry(int key, V value, Entry<V> next) {
this.key = key;
this.value = value;
this.next = next;
}
protected Object clone() {
return new Entry<V>(key, value, (next == null ? null : (Entry<V>) next.clone()));
}
// Map.Entry Ops
public Integer getKey() {
return (objectKey != null) ? objectKey : (objectKey = Integer.valueOf(key));
}
public V getValue() {
return value;
}
public V setValue(V value) {
V oldValue = this.value;
this.value = value;
return oldValue;
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry) o;
return (getKey().equals(e.getKey())) &&
(value==null ? e.getValue()==null : value.equals(e.getValue()));
}
public int hashCode() {
return key ^ (value==null ? 0 : value.hashCode());
}
public String toString() {
return String.valueOf(key) + "=" + value;
}
}
// Types of Iterators
private static final int KEYS = 0;
private static final int VALUES = 1;
private static final int ENTRIES = 2;
private class IntHashIterator implements Iterator {
Entry[] table = IntHashMap.this.table;
int index = table.length;
Entry entry;
Entry lastReturned;
int type;
/**
* The modCount value that the iterator believes that the backing
* List should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
IntHashIterator(int type) {
this.type = type;
}
public boolean hasNext() {
while (entry == null && index > 0) {
entry = table[--index];
}
return entry != null;
}
public Object next() {
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
while (entry == null && index > 0) {
entry = table[--index];
}
if (entry != null) {
Entry e = lastReturned = entry;
entry = e.next;
return type == KEYS ? e.getKey() : (type == VALUES ? e.value : e);
}
throw new NoSuchElementException();
}
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
Entry<V>[] tab = IntHashMap.this.table;
int index = (lastReturned.key & 0x7fffffff) % tab.length;
for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e == lastReturned) {
modCount++;
expectedModCount++;
if (prev == null) {
tab[index] = e.next;
} else {
prev.next = e.next;
}
count--;
lastReturned = null;
return;
}
}
throw new ConcurrentModificationException();
}
}
/**
* Save the state of the <tt>IntHashMap</tt> instance to a stream (i.e.,
* serialize it).
*
* @serialData The <i>capacity</i> of the IntHashMap (the length of the
* bucket array) is emitted (int), followed by the
* <i>size</i> of the IntHashMap (the number of key-value
* mappings), followed by the key (Object) and value (Object)
* for each key-value mapping represented by the IntHashMap
* The key-value mappings are emitted in no particular order.
*/
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
// Write out the threshold, loadfactor, and any hidden stuff
s.defaultWriteObject();
// Write out number of buckets
s.writeInt(table.length);
// Write out size (number of Mappings)
s.writeInt(count);
// Write out keys and values (alternating)
for (int index = table.length - 1; index >= 0; index--) {
Entry entry = table[index];
while (entry != null) {
s.writeInt(entry.key);
s.writeObject(entry.value);
entry = entry.next;
}
}
}
/**
* Reconstitute the <tt>IntHashMap</tt> instance from a stream (i.e.,
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException
{
// Read in the threshold, loadfactor, and any hidden stuff
s.defaultReadObject();
// Read in number of buckets and allocate the bucket array;
int numBuckets = s.readInt();
table = new Entry[numBuckets];
// Read in size (number of Mappings)
int size = s.readInt();
// Read the keys and values, and put the mappings in the IntHashMap
for (int i=0; i<size; i++) {
int key = s.readInt();
V value = (V) s.readObject();
put(key, value);
}
}
int capacity() {
return table.length;
}
float loadFactor() {
return loadFactor;
}
}
Related examples in the same category