gov.nasa.worldwind.util

Class BoundedHashMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<K,V>

gov.nasa.worldwind.util.BoundedHashMap<K,V>

Type Parameters:

K - The map key type.

V - The map value type.

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map<K,V>

public class BoundedHashMap<K,V>
extends java.util.LinkedHashMap<K,V>

BoundedHashMap is a map with a fixed capacity. When the map's size exceeds its capacity, it automatically removes elements until its size is equal to its capacity.

BoundedHashMap can operate in two ordering modes: insertion order and access order. The mode specified which entries are automatically removed when the map is over capacity. In insertion order mode the map removes the eldest entry (the first entry added). In access order mode, the map automatically removes the least recently used entry.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	DEFAULT_CAPACITY
protected static float	DEFAULT_LOAD_FACTOR

Constructor Summary

Constructors

Constructor and Description
BoundedHashMap() Creates a BoundedHashMap with a capacity of 16, in insertion order mode.
BoundedHashMap(int capacity) Creates a BoundedHashMap with a specified maximum capacity, in insertion order mode.
BoundedHashMap(int capacity, boolean accessOrder) Creates a BoundedHashMap with a specified maximum capacity and ordering mode.

Method Summary

Modifier and Type	Method and Description
int	getCapacity() Returns the maximum number of entries in the map.
protected static int	getInitialCapacity(int capacity, float loadFactor)
protected boolean	removeEldestEntry(java.util.Map.Entry<K,V> eldest)
protected void	removeOverCapacityEntries() Removes the first n entries in the map, where n is the number of entries in the map beyond its capacity.
void	setCapacity(int capacity) Sets the maximum number of entries in the map.

Methods inherited from class java.util.LinkedHashMap

clear, containsValue, entrySet, forEach, get, getOrDefault, keySet, replaceAll, values

Methods inherited from class java.util.HashMap

clone, compute, computeIfAbsent, computeIfPresent, containsKey, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, containsKey, equals, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size

Field Detail

DEFAULT_CAPACITY

protected static final int DEFAULT_CAPACITY

See Also:

Constant Field Values

DEFAULT_LOAD_FACTOR

protected static final float DEFAULT_LOAD_FACTOR

See Also:

Constant Field Values

Constructor Detail

BoundedHashMap

public BoundedHashMap()

Creates a BoundedHashMap with a capacity of 16, in insertion order mode.

BoundedHashMap

public BoundedHashMap(int capacity)

Creates a BoundedHashMap with a specified maximum capacity, in insertion order mode.

Parameters:

capacity - the maximum number of entries in the map.

BoundedHashMap

public BoundedHashMap(int capacity,
                      boolean accessOrder)

Creates a BoundedHashMap with a specified maximum capacity and ordering mode.

Parameters:

capacity - the maximum number of entries in the map.

accessOrder - the ordering mode: true specifies access order, false specifies insertion order.

Method Detail

getCapacity

public int getCapacity()

Returns the maximum number of entries in the map.

Returns:

maximum number of entries in the map.

getInitialCapacity

protected static int getInitialCapacity(int capacity,
                                        float loadFactor)

removeEldestEntry

protected boolean removeEldestEntry(java.util.Map.Entry<K,V> eldest)

Overrides:

removeEldestEntry in class java.util.LinkedHashMap<K,V>

removeOverCapacityEntries

protected void removeOverCapacityEntries()

Removes the first n entries in the map, where n is the number of entries in the map beyond its capacity. Note that the entry set and the corresponding iterator are backed by the map itself, so changes to an entry iterator correspond to changes in the map. We use the iterator's remove() method because we're removing elements from the entry set as we iterate over them.

setCapacity

public void setCapacity(int capacity)

Sets the maximum number of entries in the map. If the new capacity is less than the map's current size, this automatically removes entries until the map's size is equal to its capacity.

Parameters:

capacity - maximum number of entries in the map.