public class Flat3Map<K,V> extends java.lang.Object implements IterableMap<K,V>, java.io.Serializable, java.lang.Cloneable
Map
implementation that stores data in simple fields until
the size is greater than 3.
This map is designed for performance and can outstrip HashMap. It also has good garbage collection characteristics.
The performance gains on puts are due to not needing to create a Map Entry object. This is a large saving not only in performance but in garbage collection.
Whilst in flat mode this map is also easy for the garbage collector to dispatch. This is because it contains no complex objects or arrays which slow the progress.
Do not use Flat3Map
if the size is likely to grow beyond 3.
Note that Flat3Map is not synchronized and is not thread-safe.
If you wish to use this map from multiple threads concurrently, you must use
appropriate synchronization. The simplest approach is to wrap this map
using Collections.synchronizedMap(Map)
. This class may throw
exceptions when accessed by concurrent threads without synchronization.
Modifier and Type | Class and Description |
---|---|
(package private) static class |
Flat3Map.EntryIterator<K,V> |
(package private) static class |
Flat3Map.EntrySet<K,V>
EntrySet
|
(package private) static class |
Flat3Map.EntrySetIterator<K,V>
EntrySetIterator and MapEntry
|
(package private) static class |
Flat3Map.FlatMapEntry<K,V> |
(package private) static class |
Flat3Map.FlatMapIterator<K,V>
FlatMapIterator
|
(package private) static class |
Flat3Map.KeySet<K>
KeySet
|
(package private) static class |
Flat3Map.KeySetIterator<K>
KeySetIterator
|
(package private) static class |
Flat3Map.Values<V>
Values
|
(package private) static class |
Flat3Map.ValuesIterator<V>
ValuesIterator
|
Modifier and Type | Field and Description |
---|---|
private AbstractHashedMap<K,V> |
delegateMap
Map, used while in delegate mode
|
private int |
hash1
Hash, used while in flat mode
|
private int |
hash2
Hash, used while in flat mode
|
private int |
hash3
Hash, used while in flat mode
|
private K |
key1
Key, used while in flat mode
|
private K |
key2
Key, used while in flat mode
|
private K |
key3
Key, used while in flat mode
|
private static long |
serialVersionUID
Serialization version
|
private int |
size
The size of the map, used while in flat mode
|
private V |
value1
Value, used while in flat mode
|
private V |
value2
Value, used while in flat mode
|
private V |
value3
Value, used while in flat mode
|
Constructor and Description |
---|
Flat3Map()
Constructor.
|
Flat3Map(java.util.Map<? extends K,? extends V> map)
Constructor copying elements from another map.
|
Modifier and Type | Method and Description |
---|---|
void |
clear()
Clears the map, resetting the size to zero and nullifying references
to avoid garbage collection issues.
|
Flat3Map<K,V> |
clone()
Clones the map without cloning the keys or values.
|
boolean |
containsKey(java.lang.Object key)
Checks whether the map contains the specified key.
|
boolean |
containsValue(java.lang.Object value)
Checks whether the map contains the specified value.
|
private void |
convertToMap()
Converts the flat map data to a map.
|
protected AbstractHashedMap<K,V> |
createDelegateMap()
Create an instance of the map used for storage when in delegation mode.
|
java.util.Set<java.util.Map.Entry<K,V>> |
entrySet()
Gets the entrySet view of the map.
|
boolean |
equals(java.lang.Object obj)
Compares this map with another.
|
V |
get(java.lang.Object key)
Gets the value mapped to the key specified.
|
int |
hashCode()
Gets the standard Map hashCode.
|
boolean |
isEmpty()
Checks whether the map is currently empty.
|
java.util.Set<K> |
keySet()
Gets the keySet view of the map.
|
MapIterator<K,V> |
mapIterator()
Gets an iterator over the map.
|
V |
put(K key,
V value)
Puts a key-value mapping into this map.
|
void |
putAll(java.util.Map<? extends K,? extends V> map)
Puts all the values from the specified map into this map.
|
private void |
readObject(java.io.ObjectInputStream in)
Read the map in using a custom routine.
|
V |
remove(java.lang.Object key)
Removes the specified mapping from this map.
|
int |
size()
Gets the size of the map.
|
java.lang.String |
toString()
Gets the map as a String.
|
java.util.Collection<V> |
values()
Gets the values view of the map.
|
private void |
writeObject(java.io.ObjectOutputStream out)
Write the map out using a custom routine.
|
private static final long serialVersionUID
private transient int size
private transient int hash1
private transient int hash2
private transient int hash3
private transient K key1
private transient K key2
private transient K key3
private transient V value1
private transient V value2
private transient V value3
private transient AbstractHashedMap<K,V> delegateMap
public V get(java.lang.Object key)
public int size()
public boolean isEmpty()
public boolean containsKey(java.lang.Object key)
public boolean containsValue(java.lang.Object value)
public void putAll(java.util.Map<? extends K,? extends V> map)
private void convertToMap()
protected AbstractHashedMap<K,V> createDelegateMap()
This can be overridden by subclasses to provide a different map implementation. Not every AbstractHashedMap is suitable, identity and reference based maps would be poor choices.
public V remove(java.lang.Object key)
public void clear()
public MapIterator<K,V> mapIterator()
A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object. It also avoids creating the Map Entry object.
mapIterator
in interface IterableGet<K,V>
public java.util.Set<java.util.Map.Entry<K,V>> entrySet()
NOTE: from 4.0, the returned Map Entry will be an independent object and will
not change anymore as the iterator progresses. To avoid this additional object
creation and simply iterate through the entries, use mapIterator()
.
public java.util.Set<K> keySet()
mapIterator()
.public java.util.Collection<V> values()
mapIterator()
.private void writeObject(java.io.ObjectOutputStream out) throws java.io.IOException
java.io.IOException
private void readObject(java.io.ObjectInputStream in) throws java.io.IOException, java.lang.ClassNotFoundException
java.io.IOException
java.lang.ClassNotFoundException
public Flat3Map<K,V> clone()
clone
in class java.lang.Object
public boolean equals(java.lang.Object obj)
public int hashCode()
public java.lang.String toString()
toString
in class java.lang.Object