javax.realtime

Enum QueueOverflowPolicy

java.lang.Object

java.lang.Enum<QueueOverflowPolicy>

javax.realtime.QueueOverflowPolicy

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<QueueOverflowPolicy>

public enum QueueOverflowPolicy
extends java.lang.Enum<QueueOverflowPolicy>

Defines the set of policies for handling overflow on event queues used by ReleaseParameters. An event queue holds a number of event arrival times with any respective payload provided with the event. A reference to the event itself is only held when it happens to be the payload, e.g., for an AsyncObjectEvent associated with a Timer.

Since:

RTSJ 2.0

Enum Constant Summary

Enum Constants

Enum Constant and Description
DISABLE Represents the "DISABLE" policy which means, when an arrival occurs, no queuing takes place, thus no overflow can happen.
EXCEPT Represents the "EXCEPT" policy which means, when an arrival occurs and its event time and payload should be queued but the queue already holds a number of event times and payloads equal to the initial queue length, the fire() method shall throw an ArrivalTimeQueueOverflowException.
IGNORE Represents the "IGNORE" policy which means, when an arrival occurs and its event time and payload should be queued, but the queue already holds a number of event times and payloads equal to the initial queue length, the arrival is ignored.
REPLACE Represents the "REPLACE" policy which means, when an arrival occurs and should be queued but the queue already holds a number of event times and payloads equal to the initial queue length, the information for this arrival replaces a previous arrival.
SAVE Represents the "SAVE" policy which means, when an arrival occurs and should be queued but the queue is full, the queue is lengthened and the arrival time and payload are saved.

Method Summary

Modifier and Type	Method and Description
static QueueOverflowPolicy	value(java.lang.String value) Converts a string into a policy type.
static QueueOverflowPolicy	valueOf(java.lang.String name) Returns the enum constant of this type with the specified name.
static QueueOverflowPolicy[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

DISABLE

public static final QueueOverflowPolicy DISABLE

Represents the "DISABLE" policy which means, when an arrival occurs, no queuing takes place, thus no overflow can happen. This policy is for instances of ActiveEvent with no payload and instances of RealtimeThread with PeriodicParameters. In contrast to IGNORE, all incoming events increment the pending fire or release count, respectively. For this reason, it may not be used with an event handler that supports an event payload or any instance of Schedulable with SporadicParameters. This policy is also the default for PeriodicParameters. Instances of RealtimeThread with null release parameters have this policy implicitly, as they do not have an event queue either.

EXCEPT

public static final QueueOverflowPolicy EXCEPT

Represents the "EXCEPT" policy which means, when an arrival occurs and its event time and payload should be queued but the queue already holds a number of event times and payloads equal to the initial queue length, the fire() method shall throw an ArrivalTimeQueueOverflowException. When fire is used within a Timer, the exception is ignored and the fire does nothing, i.e., it acts the same as ``IGNORE''.

IGNORE

public static final QueueOverflowPolicy IGNORE

Represents the "IGNORE" policy which means, when an arrival occurs and its event time and payload should be queued, but the queue already holds a number of event times and payloads equal to the initial queue length, the arrival is ignored.

REPLACE

public static final QueueOverflowPolicy REPLACE

Represents the "REPLACE" policy which means, when an arrival occurs and should be queued but the queue already holds a number of event times and payloads equal to the initial queue length, the information for this arrival replaces a previous arrival. When the queue length is zero, the behavior is the same as the "IGNORE" policy.

SAVE

public static final QueueOverflowPolicy SAVE

Represents the "SAVE" policy which means, when an arrival occurs and should be queued but the queue is full, the queue is lengthened and the arrival time and payload are saved. This policy does not update the"initial queue length" as it alters the actual queue length. Since the SAVE policy grows the arrival time queue as necessary, for the SAVE policy the initial queue length is only an optimization. It is also the default for AperiodicParameters.

Method Detail

values

public static QueueOverflowPolicy[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (QueueOverflowPolicy c : QueueOverflowPolicy.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static QueueOverflowPolicy valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

value

public static QueueOverflowPolicy value(java.lang.String value)

Converts a string into a policy type.

Parameters:

value - is the string to convert.

Returns:

the corresponding policy type.