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实现:
package creative.air.datastructure.map; import java.util.Iterator; import java.util.Map; import java.util.Set; import java.util.concurrent.TimeUnit; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock; import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock; import java.util.logging.Level; import java.util.logging.Logger; import creative.air.datastructure.map.AirHashMap.AirEntry; /** * * @author Eric Han [email protected] 06/09/2012 * @since 0.0.1 * @version 0.0.1 */ public class HashMapCache<H, L> { enum ConcurrentStrategy { NOTIFY, WAIT, TIMEOUT } enum FullStrategy { NOTIFY, DISCARD, REPLACE } static final Logger logger = Logger.getLogger(HashMapCache.class.getName()); // cache full strategy private int capacity = 12; private FullStrategy fullStrategy = FullStrategy.NOTIFY; // cache lock strategy private static ReentrantReadWriteLock lock = new ReentrantReadWriteLock(); private static WriteLock wLock = lock.writeLock(); private static ReadLock rLock = lock.readLock(); private ConcurrentStrategy concurrentStrategy = ConcurrentStrategy.TIMEOUT; private long waitingLockTimeout = 500; private AirHashMap<H, L> map; public HashMapCache() { map = new AirHashMap<H, L>(); } public HashMapCache(int capacity) { this.capacity = capacity; map = new AirHashMap<H, L>(); } public HashMapCache(int capacity, int initialCapacity, float loadFactor) { this.capacity = capacity; map = new AirHashMap<H, L>(initialCapacity, loadFactor); } public void clear() { try { lock(wLock);// tryLock(long timeout, TimeUnit unit) map.clear(); } catch (Exception e) { logger.log(Level.SEVERE, "clear error", e); } finally { wLock.unlock(); } } public void remove(H key) { try { lock(wLock); map.remove(key); } catch (Exception e) { logger.log(Level.SEVERE, "clear error", e); } finally { wLock.unlock(); } } public L put(H key, L value) throws Exception { lock(wLock); if (this.capacity < map.size()) { switch (fullStrategy) { case NOTIFY: throw new Exception("100 reached the cache's maximum"); case DISCARD: return null; case REPLACE: // TODO it's a dangerous way // which cannot guarantee the data already stored in cache AirEntry<H, L> entry = map.getTable()[0]; remove(entry.getKey()); default: throw new Exception("100 reached the cache's maximum"); } } try { return map.put(key, value); } catch (Exception e) { logger.log(Level.SEVERE, "put error", e); return null; } finally { wLock.unlock(); } } public L get(H key) { try { lock(rLock); return map.get(key); } catch (Exception e) { logger.log(Level.SEVERE, "get error", e); return null; } finally { rLock.unlock(); } } public Iterator<Map.Entry<H, L>> iterate() { try { lock(rLock); return map.entrySet().iterator(); } catch (Exception e) { logger.log(Level.SEVERE, "get error", e); return null; } finally { rLock.unlock(); } } private void lock(Lock lock) throws Exception { switch (concurrentStrategy) { case NOTIFY: throw new Exception("200 Cannot control the cache"); case WAIT: lock.lock(); break; case TIMEOUT: lock.tryLock(waitingLockTimeout, TimeUnit.MICROSECONDS); break; } } public Set<Map.Entry<H, L>> entrySet() { return map.entrySet(); } public int getCapacity() { return capacity; } public ConcurrentStrategy getConcurrentStrategy() { return concurrentStrategy; } public FullStrategy getFullStrategy() { return fullStrategy; } public void setCapacity(int capacity) { this.capacity = capacity; } public void setConcurrentStrategy(ConcurrentStrategy concurrentStrategy) { this.concurrentStrategy = concurrentStrategy; } public void setFullStrategy(FullStrategy fullStrategy) { this.fullStrategy = fullStrategy; } public long getWaitingLockTimeout() { return waitingLockTimeout; } public void setWaitingLockTimeout(long waitingLockTimeout) { this.waitingLockTimeout = waitingLockTimeout; } }
hashmap:
package creative.air.datastructure.map; /** * * @author * Eric Han [email protected] * 16/09/2012 * @since 0.0.1 * @version 0.0.1 */ import java.io.IOException; import java.io.Serializable; import java.util.AbstractCollection; import java.util.AbstractMap; import java.util.AbstractSet; import java.util.ConcurrentModificationException; import java.util.Iterator; import java.util.Map; import java.util.NoSuchElementException; import java.util.Set; public class AirHashMap<K, V> extends AbstractMap<K, V> implements Map<K, V>, Cloneable, Serializable { private static final long serialVersionUID = 3476735979928755996L; static final int DEFAULT_INITIAL_CAPACITY = 16;// 初始容量 static final int MAXIMUM_CAPACITY = 1 << 30; static final float DEFAULT_LOAD_FACTOR = 0.75f;// 负载因子 transient AirEntry<K, V>[] table;// hash数组 transient int size; int threshold;// 阈值 final float loadFactor; transient int modCount;// 修改次数 public AirHashMap(int initialCapacity, float loadFactor) { 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; threshold = (int) (capacity * loadFactor); table = new AirEntry[capacity]; init(); } public AirHashMap(int initialCapacity) { this(initialCapacity, DEFAULT_LOAD_FACTOR); } public AirHashMap() { this.loadFactor = DEFAULT_LOAD_FACTOR; threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR); table = new AirEntry[DEFAULT_INITIAL_CAPACITY]; init(); } public AirHashMap(Map<? extends K, ? extends V> m) { this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR); putAllForCreate(m); } void init() { } static int hash(int h) { // This function ensures that hashCodes that differ only by // constant multiples at each bit position have a bounded // number of collisions (approximately 8 at default load factor). h ^= (h >>> 20) ^ (h >>> 12); return h ^ (h >>> 7) ^ (h >>> 4); } static int indexFor(int h, int length) { return h & (length - 1); } public int size() { return size; } public boolean isEmpty() { return size == 0; } public V get(Object key) { if (key == null) return getForNullKey(); int hash = hash(key.hashCode()); for (AirEntry<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))) return e.value; } return null; } private V getForNullKey() { for (AirEntry<K, V> e = table[0]; e != null; e = e.next) { if (e.key == null) return e.value; } return null; } public boolean containsKey(Object key) { return getEntry(key) != null; } final AirEntry<K, V> getEntry(Object key) { int hash = (key == null) ? 0 : hash(key.hashCode()); for (AirEntry<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)))) return e; } return null; } public V put(K key, V value) { if (key == null) return putForNullKey(value); int hash = hash(key.hashCode()); int i = indexFor(hash, table.length); for (AirEntry<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); return null; } private V putForNullKey(V value) { for (AirEntry<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; } 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 (AirEntry<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); } private void putAllForCreate(Map<? extends K, ? extends V> m) { for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) putForCreate(e.getKey(), e.getValue()); } void resize(int newCapacity) { AirEntry[] oldTable = table; int oldCapacity = oldTable.length; if (oldCapacity == MAXIMUM_CAPACITY) { threshold = Integer.MAX_VALUE; return; } AirEntry[] newTable = new AirEntry[newCapacity]; transfer(newTable); table = newTable; threshold = (int) (newCapacity * loadFactor); } void transfer(AirEntry[] newTable) { AirEntry[] src = table; int newCapacity = newTable.length; for (int j = 0; j < src.length; j++) { AirEntry<K, V> e = src[j]; if (e != null) { src[j] = null; do { AirEntry<K, V> next = e.next; int i = indexFor(e.hash, newCapacity); e.next = newTable[i]; newTable[i] = e; e = next; } while (e != null); } } } public void putAll(Map<? extends K, ? extends V> m) { int numKeysToBeAdded = m.size(); if (numKeysToBeAdded == 0) return; 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 (Map.Entry<? extends K, ? extends V> e : m.entrySet()) put(e.getKey(), e.getValue()); } public V remove(Object key) { AirEntry<K, V> e = removeEntryForKey(key); return (e == null ? null : e.value); } final AirEntry<K, V> removeEntryForKey(Object key) { int hash = (key == null) ? 0 : hash(key.hashCode()); int i = indexFor(hash, table.length); AirEntry<K, V> prev = table[i]; AirEntry<K, V> e = prev; while (e != null) { AirEntry<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; } final AirEntry<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); AirEntry<K, V> prev = table[i]; AirEntry<K, V> e = prev; while (e != null) { AirEntry<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; } public void clear() { modCount++; AirEntry[] tab = table; for (int i = 0; i < tab.length; i++) tab[i] = null; size = 0; } public boolean containsValue(Object value) { if (value == null) return containsNullValue(); AirEntry[] tab = table; for (int i = 0; i < tab.length; i++) for (AirEntry e = tab[i]; e != null; e = e.next) if (value.equals(e.value)) return true; return false; } private boolean containsNullValue() { AirEntry[] tab = table; for (int i = 0; i < tab.length; i++) for (AirEntry e = tab[i]; e != null; e = e.next) if (e.value == null) return true; return false; } public Object clone() { AirHashMap<K, V> result = null; try { result = (AirHashMap<K, V>) super.clone(); } catch (CloneNotSupportedException e) { // assert false; } result.table = new AirEntry[table.length]; result.entrySet = null; result.modCount = 0; result.size = 0; result.init(); result.putAllForCreate(this); return result; } void addEntry(int hash, K key, V value, int bucketIndex) { AirEntry<K, V> e = table[bucketIndex]; table[bucketIndex] = new AirEntry<K, V>(hash, key, value, e); if (size++ >= threshold) resize(2 * table.length); } void createEntry(int hash, K key, V value, int bucketIndex) { AirEntry<K, V> e = table[bucketIndex]; table[bucketIndex] = new AirEntry<K, V>(hash, key, value, e); size++; } 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(); } private transient Set<Map.Entry<K, V>> entrySet = null; // public Set<K> keySet() { // Set<K> ks = keySet; // return (ks != null ? ks : (keySet = new KeySet())); // } private 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 AirHashMap.this.removeEntryForKey(o) != null; } public void clear() { AirHashMap.this.clear(); } } // 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() { AirHashMap.this.clear(); } } 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(); } public boolean contains(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry<K, V> e = (Map.Entry<K, V>) o; AirEntry<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() { AirHashMap.this.clear(); } } 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) { while (i.hasNext()) { Map.Entry<K, V> e = i.next(); s.writeObject(e.getKey()); s.writeObject(e.getValue()); } } } 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 AirEntry[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 AirHashMap 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; } // ====Entry==== static class AirEntry<K, V> implements Map.Entry<K, V> { final K key; V value; AirEntry<K, V> next; final int hash; /** * Creates new entry. */ AirEntry(int h, K k, V v, AirEntry<K, V> n) { value = v; next = n; key = k; hash = h; } public final K getKey() { return key; } public final V getValue() { return value; } public final V setValue(V newValue) { V oldValue = value; value = newValue; return oldValue; } public final boolean equals(Object o) { if (!(o instanceof Map.Entry)) return false; 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 final int hashCode() { return (key == null ? 0 : key.hashCode()) ^ (value == null ? 0 : value.hashCode()); } public final 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 AirHashMap. */ void recordAccess(AirHashMap<K, V> m) { } /** * This method is invoked whenever the entry is removed from the table. */ void recordRemoval(AirHashMap<K, V> m) { } } // ====HashIterator==== private abstract class HashIterator<E> implements Iterator<E> { AirEntry<K, V> next; // next entry to return int expectedModCount; // For fast-fail int index; // current slot AirEntry<K, V> current; // current entry HashIterator() { expectedModCount = modCount; if (size > 0) { // advance to first entry AirEntry[] t = table; while (index < t.length && (next = t[index++]) == null) ; } } public final boolean hasNext() { return next != null; } final AirEntry<K, V> nextEntry() { if (modCount != expectedModCount) throw new ConcurrentModificationException(); AirEntry<K, V> e = next; if (e == null) throw new NoSuchElementException(); if ((next = e.next) == null) { AirEntry[] t = table; while (index < t.length && (next = t[index++]) == null) ; } current = e; return e; } public void remove() { if (current == null) throw new IllegalStateException(); if (modCount != expectedModCount) throw new ConcurrentModificationException(); Object k = current.key; current = null; AirHashMap.this.removeEntryForKey(k); expectedModCount = modCount; } } public AirEntry<K, V>[] getTable() { return table; } }
测试:
package creative.air.datastructure.map; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.logging.Level; import java.util.logging.Logger; import junit.framework.Assert; import org.junit.Test; /** * Test HashMap * 1 map:键值对 hash:hashcode * 2 非线程安全 键值允许为空 键为空时的处理 * 3 数组+链表结构 * 4 负载因子loadFactor和阈值threshold 扩容机制 缓存设计 * 5 遍历 * * Test Cache * @author * Eric Han [email protected] * 06/09/2012 * @since 0.0.1 * @version 0.0.1 */ public class HashMapTest { static final Logger logger = Logger.getLogger(HashMapTest.class.getName()); @Test public void test2() throws Exception { HashMapCache<String, Integer> cacheMap = new HashMapCache<String, Integer>(); cacheMap.clear(); cacheMap.put("" + 1, null); cacheMap.put(null, 1); cacheMap.put(null, null); Assert.assertNull(cacheMap.get(null)); } @Test public void test5() { int n = 0; final int maxium = 5000; HashMapCache<String, Integer> cacheMap = new HashMapCache<String, Integer>(maxium); HashMapCache<String, Integer> retrievingMap = new HashMapCache<String, Integer>(maxium, maxium / 10, 0.5f); boolean inputRight = true; while (n < maxium) { String s = "" + n; try { cacheMap.put(s, n); retrievingMap.put(s, n++); } catch (Exception e) { e.printStackTrace(); inputRight = false; break; } } Assert.assertTrue(inputRight); Object[] r1 = iterate(cacheMap, Level.INFO); Object[] r2 = iterate(retrievingMap, Level.INFO); logger.log(Level.INFO, "default map iterating elapse:{0}(start={1},end={2})", r1); logger.log(Level.INFO, "customize map iterating elapse:{0}(start={1},end={2})", r2); Assert.assertTrue((Long) r1[0] >= (Long) r2[0]); } /** * @param level * */ private Object[] iterate(HashMapCache<String, Integer> map, Level level) { Iterator<Map.Entry<String, Integer>> iter = map.entrySet().iterator(); long startTime = System.currentTimeMillis(); while (iter.hasNext()) { Map.Entry<String, Integer> entry = iter.next(); String key = entry.getKey(); Integer val = entry.getValue(); logger.log(level, "{0}:{1}", new Object[] { key, val }); } long endTime = System.currentTimeMillis(); return new Object[] { endTime - startTime, endTime, startTime }; } @Test public void testPutAll(){ HashMap<String,String> map=new HashMap<String,String>(); HashMap<String,HashMap<String,String>> map2=new HashMap<String,HashMap<String,String>>(); map.put("Gateway", "Thomson"); map2.put("patner", map); map.put("Gateway", "Technicolor"); Iterator<Map.Entry<String,HashMap<String,String>>> iter = map2.entrySet().iterator(); while (iter.hasNext()) { Map.Entry<String,HashMap<String,String>> entry = iter.next(); String key = entry.getKey(); HashMap<String,String> val = entry.getValue(); Iterator<Map.Entry<String,String>> iter2 = val.entrySet().iterator(); while (iter.hasNext()) { Map.Entry<String,String> entry2 = iter2.next(); String key2 = entry2.getKey(); String val2 = entry2.getValue(); Assert.assertEquals("Technicolor", val2); logger.log(Level.INFO, "{0}:{1}", new Object[] { key2, val2 }); } logger.log(Level.INFO, "{0}:{1}", new Object[] { key, val }); } } }