com.nt.udc.util.state

Class StateFreezeHelper

java.lang.Object

com.nt.udc.util.state.StateFreezeHelper

public class StateFreezeHelper
extends java.lang.Object

This class is intended for use within a class that has implemented the StateFreezable interface. It encapsulates some of the key state freezing behaviors, specifically the relationship between the freezing of the main processing, and the unfreezing by the unfreeze() method.
To use this class, several of the methods must be called in the appropriate places in the methods of the StateFreezable interface.
"freeze()" should be used in the implementation of StateFreezable.freezeState(). It will cause any call to "checkFreezeAndWait()" to halt within that method, effectively stopping that Thread.
"checkFreezeAndWait()" should be used in the main processing thread that one wishes to freeze. At the appropriate place, call this method, and it will halt the thread if "freeze()" has been called previously. Otherwise, it will return, and the prcessing thread will process normally. It will halt in this method until the "unfreeze()" method is called, preferably in the StateFreezable.unfreezeState() method.
"unfreeze()" should be used in the implementation of StateFreezble.unfreezeState(). It is responsible for resuming the thread previously halted in the "checkFreezeAndWait()" method.
Note that the implementation of "checkFreezeAndWait()" uses Object.wait(), and "unfreeze()" uses Object.notify().

Constructor Summary

Constructors

Constructor and Description
StateFreezeHelper(LoggerIfc logger) Constructs the StateFreezeHelper with a logger for unexpected errors.

Method Summary

Methods

Modifier and Type	Method and Description
void	checkFreezeAndWait() Checks if the StateFreezeHelper's state is frozen, and halts the current thread if it is.
void	freeze(Callback freezeCompleted) Changes the StateFreezeHelper to a "frozen" state.
void	unfreeze() Changes the StateFreezeHelper to an "unfrozen" state, and resumes all processing previously halted in "checkFreezeAndWait()".

Methods inherited from class java.lang.Object

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

Constructor Detail

StateFreezeHelper

public StateFreezeHelper(LoggerIfc logger)

Constructs the StateFreezeHelper with a logger for unexpected errors.

Parameters:

logger - Logger for errors.

Method Detail

freeze

public void freeze(Callback freezeCompleted)

Changes the StateFreezeHelper to a "frozen" state. All calls to "checkFreezeAndWait()" will halt in that method when this method has been called.
The Callback should be the Callback received from StateFreezable.freezeState().

Parameters:

freezeCompleted - The callback to notify the StateManager that the processing has been frozen.

unfreeze

public void unfreeze()

Changes the StateFreezeHelper to an "unfrozen" state, and resumes all processing previously halted in "checkFreezeAndWait()".
Note: This method uses Object.notify() as part of its implementation.

checkFreezeAndWait

public void checkFreezeAndWait()

Checks if the StateFreezeHelper's state is frozen, and halts the current thread if it is. The StateFreezeHelper is considered "frozen" if "freeze()" has been called previously. If "frozen", the current thread will be halted until "unfreeze()" is called on a different thread. Once "unfreeze()" has been called, processing resumes normally on the current thread.
Note: This method uses Object.wait() as part of its implementation.