Class MemoryStateStore

java.lang.Object

com.wualabs.qtsurfer.engine.core.state.MemoryStateStore

All Implemented Interfaces:

StateStore

public class MemoryStateStore
extends Object
implements StateStore

KV on memory State store implementation

Constructor Summary

Constructors

Constructor	Description
MemoryStateStore()

Method Summary

Modifier and Type	Method	Description
void	clear()
<T> T	getOrCreateState(String key, Supplier<T> factory)	Atomic lazy creation via ConcurrentHashMap.computeIfAbsent(K, Function): two threads racing the first inc()/add() on a key are guaranteed the SAME counter/accumulator instance.
<T> T	getState(String key)
<T> void	setState(String key, T value)	Sets a state value for the given key.
String	toString()

Methods inherited from class Object

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

Methods inherited from interface StateStore

add, clear, dec, getAccumulator, getCounter, getState, has, inc, is, reset, set, set, unset

Constructor Details

MemoryStateStore

public MemoryStateStore()

Method Details

setState

public <T> void setState(String key,
 T value)

Sets a state value for the given key. If value is null, the key is removed from the store. Uses a ConcurrentHashMap for thread-safe access.

Specified by:

setState in interface StateStore

Parameters:

key - the state key

value - the value to store, or null to remove the key

getState

public <T> T getState(String key)

Specified by:

getState in interface StateStore

getOrCreateState

public <T> T getOrCreateState(String key,
 Supplier<T> factory)

Atomic lazy creation via ConcurrentHashMap.computeIfAbsent(K, Function): two threads racing the first inc()/add() on a key are guaranteed the SAME counter/accumulator instance. The interface's default (check-then-put) could hand each racer its own instance, losing the increments applied to the discarded one — despite the accessors' documented thread-safety.

Specified by:

getOrCreateState in interface StateStore

Parameters:

key - the state key

factory - creates the value when absent

Returns:

the stored value (never null)

clear

public void clear()

Specified by:

clear in interface StateStore

toString

public String toString()

Overrides:

toString in class Object