org.openjdk.jmc.common.collection

Class KeyInValueMap<K,V>

java.lang.Object

org.openjdk.jmc.common.collection.KeyInValueMap<K,V>

Type Parameters:

K - key type

V - value type

All Implemented Interfaces:

Iterable<V>

Direct Known Subclasses:

EntryHashMap

public abstract class KeyInValueMap<K,V>
extends Object
implements Iterable<V>

A map for values that has the key inside the value, so only storing the value directly without a wrapping map entry is sufficient. It can also compute absent values which is not available in Java 7 maps.

Does not support null keys or values. Not thread safe.

Constructor Summary

Constructors

Constructor and Description
KeyInValueMap(int initialCapacity, float loadFactor) Create a new map.

Method Summary

Modifier and Type	Method and Description
protected abstract V	computeValue(K key) This method must be overridden in subclasses so that values can be computed for missing keys.
V	get(K key, boolean computeIfAbsent) Get the value for a key and optionally compute a new value if it is not already present in the map.
protected abstract K	getKey(V value) Get the key for a value.
protected int	hashKey(K key) Calculate the hash for a key.
Iterator<V>	iterator()
int	size()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

KeyInValueMap

public KeyInValueMap(int initialCapacity,
                     float loadFactor)

Create a new map.

Parameters:

initialCapacity - initial storage capacity

loadFactor - load factor at which to increase the internal storage capacity

Method Detail

get

public V get(K key,
             boolean computeIfAbsent)

Get the value for a key and optionally compute a new value if it is not already present in the map. Automatic value computation is done with computeValue(Object) which must be implemented by subclasses.

Parameters:

key - key

computeIfAbsent - If a value is not found and this is set to true, then compute and add a new value using computeValue(Object).

Returns:

The value for the key. If computeIfAbsent is false and no matching value exists, then null is returned.

size

public int size()

iterator

public Iterator<V> iterator()

Specified by:

iterator in interface Iterable<V>

computeValue

protected abstract V computeValue(K key)

This method must be overridden in subclasses so that values can be computed for missing keys. Called by get(Object, boolean) when the requested key is missing in the map.

Parameters:

key - key to calculate value for

Returns:

calculated value

hashKey

protected int hashKey(K key)

Calculate the hash for a key. May be overridden by subclasses.

Parameters:

key - key to calculate hash for

Returns:

hash for key

getKey

protected abstract K getKey(V value)

Get the key for a value.

Parameters:

value - value to get key for

Returns:

key for value