org.codefx.libfx.concurrent.when

Class ExecuteOnceWhen<T>

java.lang.Object

org.codefx.libfx.concurrent.when.ExecuteOnceWhen<T>

Type Parameters:

T - the type the observed ObservableValue's wraps

public class ExecuteOnceWhen<T>
extends Object

Executes an action when an ObservableValue's value fulfills a certain condition.

The action will not be executed before executeWhen() is called. The action is only executed once. If it was not yet executed, this can be prevented by calling cancel().

This class guarantees that regardless of the way different threads interact with the ObservableValue the action will be executed...

• ... if the value held when executeWhen() returns passes the condition
• ... if a new value passes the condition (either during executeWhen() or after it returns)
• ... at most once

If the observable is manipulated by several threads, this class does not guarantee that the first value to pass the condition is the one handed to the action. Depending on the interaction of those threads it might be the initial value (the one tested during executeWhen()) or one of several which were set by those threads.

Use ExecuteWhen to build an instance of this class.

Method Summary

Modifier and Type	Method and Description
void	cancel() Cancels the future execution of the action.
void	executeWhen() Executes the action (once) when the observable's value passes the condition.

Methods inherited from class java.lang.Object

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

Method Detail

executeWhen

public void executeWhen()
                 throws IllegalStateException

Executes the action (once) when the observable's value passes the condition.

This is a one way function that must only be called once. Calling it again throws an IllegalStateException.

Call cancel() to prevent future execution.

Throws:

IllegalStateException - if this method is called more than once

cancel

public void cancel()

Cancels the future execution of the action. If executeWhen() was not yet called or the action was already executed, this is a no-op.