package org.rr.commons.collection;
import java.io.IOException;
import java.io.Serializable;
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;
/**
* A {@link AbstractMap} implementation which automatically remove values which
* are too
*
* @param <K>
* @param <V>
*/
public class VolatileHashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable {
/**
* 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<K,V> [] 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;
/**
*
* @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;
/**
* Each of these fields are initialized to contain an instance of the appropriate view the first time this view is requested. The views are stateless, so
* there's no reason to create more than one of each.
*/
transient volatile Set<K> keySet = null;
transient volatile Collection<V> values = null;
/**
* Specifies the max guaranteed capacity. If the maximum is reached, these values which are the oldes ones will be removed from the {@link VolatileHashMap}.
*/
int maxCapacity = -1;
/**
* Percentage value allowed to exceed the maxCapacity before the oldest data gets removed.
*/
private int volatileExceedValue = 10;
/**
* The latest entry for a successfull {@link #containsKey(Object)} is stored here.
* the next {@link #get(Object)} call will check this value first before searching
* for it.
*/
private Entry<K, V> lastContains = null;
/**
* 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.
*/
@SuppressWarnings("unchecked")
private VolatileHashMap(int maxCapacity, int initialCapacity, float loadFactor) {
if(maxCapacity < -1) {
throw new IllegalArgumentException("max capcacity of " + String.valueOf(maxCapacity) + " not supported.");
}
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal initial capacity: " + initialCapacity);
}
if (initialCapacity > MAXIMUM_CAPACITY) {
initialCapacity = MAXIMUM_CAPACITY;
}
if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Illegal load factor: " + loadFactor);
}
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity) {
capacity <<= 1;
}
this.loadFactor = loadFactor;
this.maxCapacity = maxCapacity;
threshold = (int) (capacity * loadFactor);
table = new Entry[capacity];
init();
}
/**
* Constructs an empty <tt>HashMap</tt> with the specified max capacity and the default load factor (0.75).
* The default init capacity is 16.
*
* @param maxCapacity
* the max capacity.
* @throws IllegalArgumentException
* if the initial capacity is negative.
*/
public VolatileHashMap(int maxCapacity) {
this(maxCapacity, DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs an empty <tt>HashMap</tt> with the specified initial capacity and the default load factor (0.75)
* and a specified maximal capacity which allows a HashMap with transient values.
*
* @param initialCapacity the initial capacity.
* @param maxCapacity the maximal capacity
* @throws IllegalArgumentException
* if the initial capacity is negative.
*
* @see #setMaxCapacity(int)
*/
public VolatileHashMap(int initialCapacity, int maxCapacity) {
this(maxCapacity, initialCapacity, DEFAULT_LOAD_FACTOR);
}
// 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() {
}
/**
* Value representing null keys inside tables.
*/
static final Object NULL_KEY = new Object();
/**
* Returns a hash value for the specified object. In addition to the object's own hashCode, this method applies a "supplemental hash function," which
* defends against poor quality hash functions. This is critical because HashMap uses power-of two length hash tables.
* <p>
*
* The shift distances in this function were chosen as the result of an automated search over the entire four-dimensional search space.
*/
static int hash(Object x) {
int h = x.hashCode();
h += ~(h << 9);
h ^= (h >>> 14);
h += (h << 4);
h ^= (h >>> 10);
return h;
}
/**
* Check for equality of non-null reference x and possibly-null y.
*/
static boolean eq(Object x, Object y) {
return x == y || x.equals(y);
}
/**
* Returns index for hash code h.
*/
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(Object, Object)
*/
public V get(Object key) {
if (key == null) {
return getForNullKey();
}
if(lastContains!=null && lastContains.key.equals(key)) {
lastContains.time = System.currentTimeMillis(); // update the time for the touched entry.
V value = lastContains.value;
lastContains = null;
return value;
}
int hash = hash(key.hashCode());
for (Entry<K,V> e = table[indexFor(hash, table.length)];
e != null;
e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
if(e!=null) {
e.time = System.currentTimeMillis(); // update the time for the touched entry.
}
return e.value;
}
}
return null;
}
/**
* Offloaded version of get() to look up null keys. Null keys map
* to index 0. This null case is split out into separate methods
* for the sake of performance in the two most commonly used
* operations (get and put), but incorporated with conditionals in
* others.
*/
private V getForNullKey() {
for (Entry<K,V> e = table[0]; e != null; e = e.next) {
if (e.key == null)
return e.value;
}
return null;
}
/**
* 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(Object key) {
return (lastContains = getEntry(key)) != null;
}
/**
* Returns the entry associated with the specified key in the HashMap. Returns null if the HashMap contains no mapping for this key.
*/
final Entry<K, V> getEntry(Object key) {
int hash = (key == null) ? 0 : hash(key.hashCode());
for (Entry<K, V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
e.time = System.currentTimeMillis(); // update the time for the touched entry.
return e;
}
}
return null;
}
/**
* 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 V put(K key, V value) {
//if the max capacity is 0, do not put anything into the map
if(maxCapacity==0) {
return null;
}
if (key == null) {
return putForNullKey(value);
}
int hash = hash(key.hashCode());
int i = indexFor(hash, table.length);
for (Entry<K,V> e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this);
return oldValue;
}
}
modCount++;
addEntry(hash, key, value, i);
removeOldEntries();
return null;
}
/**
* Offloaded version of put for null keys
*/
private V putForNullKey(V value) {
for (Entry<K,V> e = table[0]; e != null; e = e.next) {
if (e.key == null) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this);
return oldValue;
}
}
modCount++;
addEntry(0, null, value, 0);
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.
*/
private void putForCreate(K key, V value) {
int hash = (key == null) ? 0 : hash(key.hashCode());
int i = indexFor(hash, 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<K,V> e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
e.value = value;
return;
}
}
createEntry(hash, key, value, i);
}
void putAllForCreate(Map<? extends K, ? extends V> m) {
for (Iterator<? extends Map.Entry<? extends K, ? extends V>> i = m.entrySet().iterator(); i.hasNext(); ) {
Map.Entry<? extends K, ? extends V> e = 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).
*/
@SuppressWarnings("unchecked")
void resize(int newCapacity) {
Entry<K,V>[] oldTable = table;
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return;
}
Entry<K,V>[] newTable = new Entry[newCapacity];
transfer(newTable);
table = newTable;
threshold = (int) (newCapacity * loadFactor);
}
/**
* Transfer all entries from current table to newTable.
*/
void transfer(Entry<K,V>[] newTable) {
Entry<K,V>[] src = table;
int newCapacity = newTable.length;
for (int j = 0; j < src.length; j++) {
Entry<K,V> e = src[j];
if (e != null) {
src[j] = null;
do {
Entry<K,V> next = e.next;
int i = indexFor(e.hash, 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(Map<? extends K, ? extends V> m) {
//if the max capacity is 0, do not put anything into the map
if(maxCapacity<=0) {
return;
}
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<? extends Map.Entry<? extends K, ? extends V>> i = m.entrySet().iterator(); i.hasNext(); ) {
Map.Entry<? extends K, ? extends V> e = i.next();
put(e.getKey(), e.getValue());
}
removeOldEntries();
}
/**
* 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(Object key) {
Entry<K,V> e = removeEntryForKey(key);
return (e == null ? null : 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.
*/
final Entry<K,V> removeEntryForKey(Object key) {
int hash = (key == null) ? 0 : hash(key.hashCode());
int i = indexFor(hash, table.length);
Entry<K,V> prev = table[i];
Entry<K,V> e = prev;
while (e != null) {
Entry<K,V> next = e.next;
Object k;
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
e.recordRemoval(this);
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Special version of remove for EntrySet.
*/
@SuppressWarnings("unchecked")
Entry<K,V> removeMapping(Object o) {
if (!(o instanceof Map.Entry)) {
return null;
}
Map.Entry<K,V> entry = (Map.Entry<K,V>) o;
Object key = entry.getKey();
int hash = (key == null) ? 0 : hash(key.hashCode());
int i = indexFor(hash, table.length);
Entry<K,V> prev = table[i];
Entry<K,V> e = prev;
while (e != null) {
Entry<K,V> next = e.next;
if (e.hash == hash && e.equals(entry)) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
e.recordRemoval(this);
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Removes all mappings from this map.
*/
public void clear() {
modCount++;
Entry<K,V> 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<K,V> tab[] = table;
for (int i = 0; i < tab.length; i++)
for (Entry<K,V> 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
*/
protected boolean containsNullValue() {
Entry<K,V> tab[] = table;
for (int i = 0; i < tab.length; i++)
for (Entry<K,V> 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.
*/
@SuppressWarnings("unchecked")
public Object clone() {
VolatileHashMap<K,V> result = null;
try {
result = (VolatileHashMap<K,V>) super.clone();
} catch (CloneNotSupportedException e) {
// assert false;
}
result.table = new Entry[table.length];
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate(this);
return result;
}
static class Entry<K,V> implements Map.Entry<K,V> {
final K key;
V value;
final int hash;
Entry<K,V> next;
long time;
/**
* Create new entry.
*/
Entry(int h, K k, V v, Entry<K,V> n) {
value = v;
next = n;
key = k;
hash = h;
time = System.currentTimeMillis();
}
public K getKey() {
return key;
}
public V getValue() {
return value;
}
public V setValue(V newValue) {
V oldValue = value;
value = newValue;
return oldValue;
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
@SuppressWarnings("rawtypes")
Map.Entry e = (Map.Entry) o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2))) {
return true;
}
}
return false;
}
public int hashCode() {
return (key == NULL_KEY ? 0 : key.hashCode()) ^ (value == null ? 0 : value.hashCode());
}
public String toString() {
return getKey() + "=" + getValue();
}
/**
* This method is invoked whenever the value in an entry is overwritten by an invocation of put(k,v) for a key k that's already in the HashMap.
*/
void recordAccess(VolatileHashMap<K,V> m) {
}
/**
* This method is invoked whenever the entry is removed from the table.
*/
void recordRemoval(VolatileHashMap<K,V> m) {
}
}
/**
* Adds 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.
*/
void addEntry(int hash, K key, V value, int bucketIndex) {
Entry<K, V> e = table[bucketIndex];
table[bucketIndex] = new Entry<K, V>(hash, key, value, e);
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.
*/
void createEntry(int hash, K key, V value, int bucketIndex) {
Entry<K, V> e = table[bucketIndex];
table[bucketIndex] = new Entry<K, V>(hash, key, value, e);
size++;
}
private abstract class HashIterator<E> implements Iterator<E> {
Entry<K,V> next; // next entry to return
int expectedModCount; // For fast-fail
int index; // current slot
Entry<K,V> current; // current entry
HashIterator() {
expectedModCount = modCount;
Entry<K,V>[] t = table;
int i = t.length;
Entry<K,V> n = null;
if (size != 0) { // advance to first entry
while (i > 0 && (n = t[--i]) == null)
;
}
next = n;
index = i;
}
public boolean hasNext() {
return next != null;
}
Entry<K,V> nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry<K,V> e = next;
if (e == null)
throw new NoSuchElementException();
Entry<K,V> n = e.next;
Entry<K,V>[] t = table;
int i = index;
while (n == null && i > 0)
n = t[--i];
index = i;
next = n;
return current = e;
}
public void remove() {
if (current == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Object k = current.key;
current = null;
VolatileHashMap.this.removeEntryForKey(k);
expectedModCount = modCount;
}
}
private final class ValueIterator extends HashIterator<V> {
public V next() {
return nextEntry().value;
}
}
private final class KeyIterator extends HashIterator<K> {
public K next() {
return nextEntry().getKey();
}
}
private final class EntryIterator extends HashIterator<Map.Entry<K,V>> {
public Map.Entry<K,V> next() {
return nextEntry();
}
}
// Subclass overrides these to alter behavior of views' iterator() method
Iterator<K> newKeyIterator() {
return new KeyIterator();
}
Iterator<V> newValueIterator() {
return new ValueIterator();
}
Iterator<Map.Entry<K,V>> newEntryIterator() {
return new EntryIterator();
}
// Views
private transient Set<Map.Entry<K,V>> 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<K> keySet() {
Set<K> ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
protected final class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return VolatileHashMap.this.removeEntryForKey(o) != null;
}
public void clear() {
VolatileHashMap.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<V> values() {
Collection<V> vs = values;
return (vs != null ? vs : (values = new Values()));
}
private final class Values extends AbstractCollection<V> {
public Iterator<V> iterator() {
return newValueIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
VolatileHashMap.this.clear();
}
}
/**
* Returns a {@link Set} view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and
* vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own <tt>remove</tt> operation, or
* through the <tt>setValue</tt> operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element
* removal, which removes the corresponding mapping from the 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 mappings contained in this map
*/
public Set<Map.Entry<K, V>> entrySet() {
return entrySet0();
}
private Set<Map.Entry<K, V>> entrySet0() {
Set<Map.Entry<K, V>> es = entrySet;
return es != null ? es : (entrySet = new EntrySet());
}
private final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
public Iterator<Map.Entry<K,V>> iterator() {
return newEntryIterator();
}
@SuppressWarnings("unchecked")
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<K,V> e = (Map.Entry<K,V>) o;
Entry<K,V> candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
public boolean remove(Object o) {
return removeMapping(o) != null;
}
public int size() {
return size;
}
public void clear() {
VolatileHashMap.this.clear();
}
}
/**
* Save the state of the <tt>HashMap</tt> instance to a stream (i.e., serialize it).
*
* @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 {
Iterator<Map.Entry<K,V>> i = (size > 0) ? entrySet0().iterator() : null;
// 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)
if (i == null)
return;
while (i.hasNext()) {
Map.Entry<K,V> e = i.next();
s.writeObject(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).
*/
@SuppressWarnings("unchecked")
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++) {
K key = (K) s.readObject();
V value = (V) s.readObject();
putForCreate(key, value);
}
}
// These methods are used when serializing HashSets
int capacity() {
return table.length;
}
float loadFactor() {
return loadFactor;
}
/**
* Gets the maximal capacity. If no maximal capacity is specified -1 is returned.
*
* @return The max capacity
* @see #setMaxCapacity(int)
*/
public int getMaxCapacity() {
return maxCapacity;
}
/**
* Sets the maximal capacity for this {@link VolatileHashMap} instance. If the max capacity is reached, the oldes values will be removed from the {@link VolatileHashMap}.
*
* @param maxCapacity
* The maximal number of entries.
* @see #getMaxCapacity()
*/
public void setMaxCapacity(int maxCapacity) {
if(maxCapacity < -1) {
throw new IllegalArgumentException("max capcacity of " + String.valueOf(maxCapacity) + " not supported.");
}
this.maxCapacity = maxCapacity;
}
/**
* Removes all entries which are the oldes ones in the HashMap. The oldes ones are these ones which stays the longest time and did not touched in younger
* time.
*/
private void removeOldEntries() {
if(maxCapacity == -1) {
return;
}
//only loop if the max capacity exceeds the 10 percent mark
if (size > maxCapacity + (maxCapacity / volatileExceedValue)) {
while (size > maxCapacity) {
long oldest = System.currentTimeMillis(); // all the other should be older!
Entry<K,V> oldestEntry = null;
Iterator<Map.Entry<K, V>> iter = entrySet().iterator();
while (iter.hasNext()) {
Entry<K,V> entry = (Entry<K, V>) iter.next();
long oldOldest = oldest;
oldest = Math.min(oldest, entry.time);
if (oldOldest != oldest) {
oldestEntry = entry;
}
}
if (oldestEntry != null) {
entrySet.remove(oldestEntry);
}
}
}
}
}