Int HashMap
/*
* $Id: ArrayListStack.java 4448 2006-02-14 20:54:57Z jonathanlocke $ $Revision:
* 4448 $ $Date: 2006-02-14 21:54:57 +0100 (di, 14 feb 2006) $
*
*
* 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.io.IOException;
import java.io.Serializable;
import java.util.AbstractCollection;
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;
/**
* This is a int hashmap that has the exact same features and interface as a
* normal Map except that the key is directly an integer. So no hash is
* calculated or key object is stored.
*
* @author jcompagner
*/
public class IntHashMap implements Cloneable, Serializable
{
transient volatile Set keySet = null;
transient volatile Collection values = null;
/**
* The default initial capacity - MUST be a power of two.
*/
static final int DEFAULT_INITIAL_CAPACITY = 16;
/**
* The maximum capacity, used if a higher value is implicitly specified by
* either of the constructors with arguments. MUST be a power of two <= 1<<30.
*/
static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The load factor used when none specified in constructor.
*/
static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* The table, resized as necessary. Length MUST Always be a power of two.
*/
transient Entry[] table;
/**
* The number of key-value mappings contained in this identity hash map.
*/
transient int size;
/**
* The next size value at which to resize (capacity * load factor).
*
* @serial
*/
int threshold;
/**
* The load factor for the hash table.
*
* @serial
*/
final float loadFactor;
/**
* The number of times this HashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the HashMap or otherwise modify its internal structure (e.g., rehash).
* This field is used to make iterators on Collection-views of the HashMap
* fail-fast. (See ConcurrentModificationException).
*/
transient volatile int modCount;
/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and load factor.
*
* @param initialCapacity
* The initial capacity.
* @param loadFactor
* The load factor.
* @throws IllegalArgumentException
* if the initial capacity is negative or the load factor is
* nonpositive.
*/
public IntHashMap(int initialCapacity, float loadFactor)
{
if (initialCapacity < 0)
{
throw new IllegalArgumentException("Illegal initial capacity: " + //$NON-NLS-1$
initialCapacity);
}
if (initialCapacity > MAXIMUM_CAPACITY)
{
initialCapacity = MAXIMUM_CAPACITY;
}
if (loadFactor <= 0 || Float.isNaN(loadFactor))
{
throw new IllegalArgumentException("Illegal load factor: " + //$NON-NLS-1$
loadFactor);
}
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity)
{
capacity <<= 1;
}
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
table = new Entry[capacity];
init();
}
/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity
* the initial capacity.
* @throws IllegalArgumentException
* if the initial capacity is negative.
*/
public IntHashMap(int initialCapacity)
{
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs an empty <tt>HashMap</tt> with the default initial capacity
* (16) and the default load factor (0.75).
*/
public IntHashMap()
{
this.loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
table = new Entry[DEFAULT_INITIAL_CAPACITY];
init();
}
// internal utilities
/**
* Initialization hook for subclasses. This method is called in all
* constructors and pseudo-constructors (clone, readObject) after HashMap
* has been initialized but before any entries have been inserted. (In the
* absence of this method, readObject would require explicit knowledge of
* subclasses.)
*/
void init()
{
}
/**
* Returns index for hash code h.
*
* @param h
* @param length
* @return The index for the hash integer for the given length
*/
static int indexFor(int h, int length)
{
return h & (length - 1);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map.
*/
public int size()
{
return size;
}
/**
* 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 size == 0;
}
/**
* Returns the value to which the specified key is mapped in this identity
* hash map, or <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 is also possible that
* the map explicitly maps the key to <tt>null</tt>. The
* <tt>containsKey</tt> method may be used to distinguish these two cases.
*
* @param key
* the key whose associated value is to be returned.
* @return the value to which this map maps the specified key, or
* <tt>null</tt> if the map contains no mapping for this key.
* @see #put(int, Object)
*/
public Object get(int key)
{
int i = indexFor(key, table.length);
Entry e = table[i];
while (true)
{
if (e == null)
{
return e;
}
if (key == e.key)
{
return e.value;
}
e = e.next;
}
}
/**
* Returns <tt>true</tt> if this map contains a mapping for the specified
* key.
*
* @param key
* The key whose presence in this map is to be tested
* @return <tt>true</tt> if this map contains a mapping for the specified
* key.
*/
public boolean containsKey(int key)
{
int i = indexFor(key, table.length);
Entry e = table[i];
while (e != null)
{
if (key == e.key)
{
return true;
}
e = e.next;
}
return false;
}
/**
* Returns the entry associated with the specified key in the HashMap.
* Returns null if the HashMap contains no mapping for this key.
*
* @param key
* @return The Entry object for the given hash key
*/
Entry getEntry(int key)
{
int i = indexFor(key, table.length);
Entry e = table[i];
while (e != null && !(key == e.key))
{
e = e.next;
}
return 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 HashMap previously associated
* <tt>null</tt> with the specified key.
*/
public Object put(int key, Object value)
{
int i = indexFor(key, table.length);
for (Entry e = table[i]; e != null; e = e.next)
{
if (key == e.key)
{
Object oldValue = e.value;
e.value = value;
return oldValue;
}
}
modCount++;
addEntry(key, value, i);
return null;
}
/**
* This method is used instead of put by constructors and pseudoconstructors
* (clone, readObject). It does not resize the table, check for
* comodification, etc. It calls createEntry rather than addEntry.
*
* @param key
* @param value
*/
private void putForCreate(int key, Object value)
{
int i = indexFor(key, table.length);
/**
* Look for preexisting entry for key. This will never happen for clone
* or deserialize. It will only happen for construction if the input Map
* is a sorted map whose ordering is inconsistent w/ equals.
*/
for (Entry e = table[i]; e != null; e = e.next)
{
if (key == e.key)
{
e.value = value;
return;
}
}
createEntry(key, value, i);
}
void putAllForCreate(IntHashMap m)
{
for (Iterator i = m.entrySet().iterator(); i.hasNext();)
{
Entry e = (Entry)i.next();
putForCreate(e.getKey(), e.getValue());
}
}
/**
* Rehashes the contents of this map into a new array with a larger
* capacity. This method is called automatically when the number of keys in
* this map reaches its threshold.
*
* If current capacity is MAXIMUM_CAPACITY, this method does not resize the
* map, but but sets threshold to Integer.MAX_VALUE. This has the effect of
* preventing future calls.
*
* @param newCapacity
* the new capacity, MUST be a power of two; must be greater than
* current capacity unless current capacity is MAXIMUM_CAPACITY
* (in which case value is irrelevant).
*/
void resize(int newCapacity)
{
Entry[] oldTable = table;
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY)
{
threshold = Integer.MAX_VALUE;
return;
}
Entry[] newTable = new Entry[newCapacity];
transfer(newTable);
table = newTable;
threshold = (int)(newCapacity * loadFactor);
}
/**
* Transfer all entries from current table to newTable.
*
* @param newTable
*/
void transfer(Entry[] newTable)
{
Entry[] src = table;
int newCapacity = newTable.length;
for (int j = 0; j < src.length; j++)
{
Entry e = src[j];
if (e != null)
{
src[j] = null;
do
{
Entry next = e.next;
int i = indexFor(e.key, newCapacity);
e.next = newTable[i];
newTable[i] = e;
e = next;
}
while (e != null);
}
}
}
/**
* Copies all of the mappings from the specified map to this map These
* mappings will replace any mappings that this map had for any of the keys
* currently in the specified map.
*
* @param m
* mappings to be stored in this map.
* @throws NullPointerException
* if the specified map is null.
*/
public void putAll(IntHashMap m)
{
int numKeysToBeAdded = m.size();
if (numKeysToBeAdded == 0)
{
return;
}
/*
* Expand the map if the map if the number of mappings to be added is
* greater than or equal to threshold. This is conservative; the obvious
* condition is (m.size() + size) >= threshold, but this condition could
* result in a map with twice the appropriate capacity, if the keys to
* be added overlap with the keys already in this map. By using the
* conservative calculation, we subject ourself to at most one extra
* resize.
*/
if (numKeysToBeAdded > threshold)
{
int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
if (targetCapacity > MAXIMUM_CAPACITY)
{
targetCapacity = MAXIMUM_CAPACITY;
}
int newCapacity = table.length;
while (newCapacity < targetCapacity)
{
newCapacity <<= 1;
}
if (newCapacity > table.length)
{
resize(newCapacity);
}
}
for (Iterator i = m.entrySet().iterator(); i.hasNext();)
{
Entry e = (Entry)i.next();
put(e.getKey(), e.getValue());
}
}
/**
* 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 Object remove(int key)
{
Entry e = removeEntryForKey(key);
return (e == null ? e : e.value);
}
/**
* Removes and returns the entry associated with the specified key in the
* HashMap. Returns null if the HashMap contains no mapping for this key.
*
* @param key
* @return The Entry object that was removed
*/
Entry removeEntryForKey(int key)
{
int i = indexFor(key, table.length);
Entry prev = table[i];
Entry e = prev;
while (e != null)
{
Entry next = e.next;
if (key == e.key)
{
modCount++;
size--;
if (prev == e)
{
table[i] = next;
}
else
{
prev.next = next;
}
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Special version of remove for EntrySet.
*
* @param o
* @return The entry that was removed
*/
Entry removeMapping(Object o)
{
if (!(o instanceof Entry))
{
return null;
}
Entry entry = (Entry)o;
int key = entry.getKey();
int i = indexFor(key, table.length);
Entry prev = table[i];
Entry e = prev;
while (e != null)
{
Entry next = e.next;
if (e.key == key && e.equals(entry))
{
modCount++;
size--;
if (prev == e)
{
table[i] = next;
}
else
{
prev.next = next;
}
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Removes all mappings from this map.
*/
public void clear()
{
modCount++;
Entry tab[] = table;
for (int i = 0; i < tab.length; i++)
{
tab[i] = null;
}
size = 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)
{
if (value == null)
{
return containsNullValue();
}
Entry tab[] = table;
for (int i = 0; i < tab.length; i++)
{
for (Entry e = tab[i]; e != null; e = e.next)
{
if (value.equals(e.value))
{
return true;
}
}
}
return false;
}
/**
* Special-case code for containsValue with null argument
*
* @return boolean true if there is a null value in this map
*/
private boolean containsNullValue()
{
Entry tab[] = table;
for (int i = 0; i < tab.length; i++)
{
for (Entry e = tab[i]; e != null; e = e.next)
{
if (e.value == null)
{
return true;
}
}
}
return false;
}
/**
* Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
* values themselves are not cloned.
*
* @return a shallow copy of this map.
*/
public Object clone() throws CloneNotSupportedException
{
IntHashMap result = null;
try
{
result = (IntHashMap)super.clone();
result.table = new Entry[table.length];
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate(this);
}
catch (CloneNotSupportedException e)
{
// assert false;
}
return result;
}
/**
* @author jcompagner
*/
public static class Entry
{
final int key;
Object value;
Entry next;
/**
* Create new entry.
*
* @param k
* @param v
* @param n
*/
Entry(int k, Object v, Entry n)
{
value = v;
next = n;
key = k;
}
/**
* @return The int key of this entry
*/
public int getKey()
{
return key;
}
/**
* @return Gets the value object of this entry
*/
public Object getValue()
{
return value;
}
/**
* @param newValue
* @return The previous value
*/
public Object setValue(Object newValue)
{
Object oldValue = value;
value = newValue;
return oldValue;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
public boolean equals(Object o)
{
if (!(o instanceof Entry))
{
return false;
}
Entry e = (Entry)o;
int k1 = getKey();
int k2 = e.getKey();
if (k1 == k2)
{
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2)))
{
return true;
}
}
return false;
}
/**
* @see java.lang.Object#hashCode()
*/
public int hashCode()
{
return key ^ (value == null ? 0 : value.hashCode());
}
/**
* @see java.lang.Object#toString()
*/
public String toString()
{
return getKey() + "=" + getValue(); //$NON-NLS-1$
}
}
/**
* Add a new entry with the specified key, value and hash code to the
* specified bucket. It is the responsibility of this method to resize the
* table if appropriate.
*
* Subclass overrides this to alter the behavior of put method.
*
* @param key
* @param value
* @param bucketIndex
*/
void addEntry(int key, Object value, int bucketIndex)
{
table[bucketIndex] = new Entry(key, value, table[bucketIndex]);
if (size++ >= threshold)
{
resize(2 * table.length);
}
}
/**
* Like addEntry except that this version is used when creating entries as
* part of Map construction or "pseudo-construction" (cloning,
* deserialization). This version needn't worry about resizing the table.
*
* Subclass overrides this to alter the behavior of HashMap(Map), clone, and
* readObject.
*
* @param key
* @param value
* @param bucketIndex
*/
void createEntry(int key, Object value, int bucketIndex)
{
table[bucketIndex] = new Entry(key, value, table[bucketIndex]);
size++;
}
private abstract class HashIterator implements Iterator
{
Entry next; // next entry to return
int expectedModCount; // For fast-fail
int index; // current slot
Entry current; // current entry
HashIterator()
{
expectedModCount = modCount;
Entry[] t = table;
int i = t.length;
Entry n = null;
if (size != 0)
{ // advance to first entry
while (i > 0 && (n = t[--i]) == null)
{
/* NoOp*/ ;
}
}
next = n;
index = i;
}
/**
* @see java.util.Iterator#hasNext()
*/
public boolean hasNext()
{
return next != null;
}
Entry nextEntry()
{
if (modCount != expectedModCount)
{
throw new ConcurrentModificationException();
}
Entry e = next;
if (e == null)
{
throw new NoSuchElementException();
}
Entry n = e.next;
Entry[] t = table;
int i = index;
while (n == null && i > 0)
{
n = t[--i];
}
index = i;
next = n;
return current = e;
}
/**
* @see java.util.Iterator#remove()
*/
public void remove()
{
if (current == null)
{
throw new IllegalStateException();
}
if (modCount != expectedModCount)
{
throw new ConcurrentModificationException();
}
int k = current.key;
current = null;
IntHashMap.this.removeEntryForKey(k);
expectedModCount = modCount;
}
}
private class ValueIterator extends HashIterator
{
/**
* @see java.util.Iterator#next()
*/
public Object next()
{
return nextEntry().value;
}
}
private class KeyIterator extends HashIterator
{
/**
* @see java.util.Iterator#next()
*/
public Object next()
{
return new Integer(nextEntry().getKey());
}
}
private class EntryIterator extends HashIterator
{
/**
* @see java.util.Iterator#next()
*/
public Object next()
{
return nextEntry();
}
}
// Subclass overrides these to alter behavior of views' iterator() method
Iterator newKeyIterator()
{
return new KeyIterator();
}
Iterator newValueIterator()
{
return new ValueIterator();
}
Iterator newEntryIterator()
{
return new EntryIterator();
}
// Views
private transient Set entrySet = 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 keySet()
{
Set ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
private class KeySet extends AbstractSet
{
/**
* @see java.util.AbstractCollection#iterator()
*/
public Iterator iterator()
{
return newKeyIterator();
}
/**
* @see java.util.AbstractCollection#size()
*/
public int size()
{
return size;
}
/**
* @see java.util.AbstractCollection#contains(java.lang.Object)
*/
public boolean contains(Object o)
{
if (o instanceof Number)
{
return containsKey(((Number)o).intValue());
}
return false;
}
/**
* @see java.util.AbstractCollection#remove(java.lang.Object)
*/
public boolean remove(Object o)
{
if (o instanceof Number)
{
return IntHashMap.this.removeEntryForKey(((Number)o).intValue()) != null;
}
return false;
}
/**
* @see java.util.AbstractCollection#clear()
*/
public void clear()
{
IntHashMap.this.clear();
}
}
/**
* 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 values()
{
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
private class Values extends AbstractCollection
{
/**
* @see java.util.AbstractCollection#iterator()
*/
public Iterator iterator()
{
return newValueIterator();
}
/**
* @see java.util.AbstractCollection#size()
*/
public int size()
{
return size;
}
/**
* @see java.util.AbstractCollection#contains(java.lang.Object)
*/
public boolean contains(Object o)
{
return containsValue(o);
}
/**
* @see java.util.AbstractCollection#clear()
*/
public void clear()
{
IntHashMap.this.clear();
}
}
/**
* 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.
* @see Map.Entry
*/
public Set entrySet()
{
Set es = entrySet;
return (es != null ? es : (entrySet = new EntrySet()));
}
private class EntrySet extends AbstractSet
{
/**
* @see java.util.AbstractCollection#iterator()
*/
public Iterator iterator()
{
return newEntryIterator();
}
/**
* @see java.util.AbstractCollection#contains(java.lang.Object)
*/
public boolean contains(Object o)
{
if (!(o instanceof Entry))
{
return false;
}
Entry e = (Entry)o;
Entry candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
/**
* @see java.util.AbstractCollection#remove(java.lang.Object)
*/
public boolean remove(Object o)
{
return removeMapping(o) != null;
}
/**
* @see java.util.AbstractCollection#size()
*/
public int size()
{
return size;
}
/**
* @see java.util.AbstractCollection#clear()
*/
public void clear()
{
IntHashMap.this.clear();
}
}
/**
* Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
* serialize it).
*
* @param s
* The ObjectOutputStream
* @throws IOException
*
* @serialData The <i>capacity</i> of the HashMap (the length of the bucket
* array) is emitted (int), followed by the <i>size</i> of the
* HashMap (the number of key-value mappings), followed by the
* key (Object) and value (Object) for each key-value mapping
* represented by the HashMap The key-value mappings are emitted
* in the order that they are returned by
* <tt>entrySet().iterator()</tt>.
*
*/
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(size);
// Write out keys and values (alternating)
for (Iterator i = entrySet().iterator(); i.hasNext();)
{
Entry e = (Entry)i.next();
s.writeInt(e.getKey());
s.writeObject(e.getValue());
}
}
private static final long serialVersionUID = 362498820763181265L;
/**
* Reconstitute the <tt>HashMap</tt> instance from a stream (i.e.,
* deserialize it).
*
* @param s
* @throws IOException
* @throws ClassNotFoundException
*/
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];
init(); // Give subclass a chance to do its thing.
// Read in size (number of Mappings)
int size = s.readInt();
// Read the keys and values, and put the mappings in the HashMap
for (int i = 0; i < size; i++)
{
int key = s.readInt();
Object value = s.readObject();
putForCreate(key, value);
}
}
// These methods are used when serializing HashSets
int capacity()
{
return table.length;
}
float loadFactor()
{
return loadFactor;
}
}
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