javax.realtime

Class RealtimeSystem

java.lang.Object

javax.realtime.RealtimeSystem

public final class RealtimeSystem
extends Object

Jamaica Real-Time Specification for Java class RealtimeSystem.

This class provides access to global status information on the real-time system and the Real-Time Specification for Java status. This includes memory related information (endianess, GC), Java monitor information and security.

Field Summary

Fields

Modifier and Type	Field and Description
static byte	BIG_ENDIAN Deprecated. RTSJ 2.0
static byte	BYTE_ORDER Deprecated. RTSJ 2.0
static byte	LITTLE_ENDIAN Deprecated. RTSJ 2.0

Method Summary

Modifier and Type	Method and Description
static boolean	canEnforceAllocationRate() Determines whether or not allocation rate enforcement is supported.
static boolean	canEnforceCost() Determines whether or not hard cost enforcement is supported.
static GarbageCollector	currentGC() currentGC returns the singleton instance of the garbage collector used by the system to recycle memory allocated in HeapMemory.
static int	getConcurrentLocksUsed() getConcurrentLocksUsed returns the number of locks that have been used concurrently by the system.
static MonitorControl	getInitialMonitorControl() Get the monitor control object of the policy that is used during system startup.
static int	getMaximumConcurrentLocks() getMaximumConcurrentLocks returns the number of locks that may be used concurrently without requiring an extra overhead (for allocating an extra monitor object or similar).
static RealtimeSecurity	getSecurityManager() Deprecated. RTSJ 2.0
static boolean	hasUniversalClock() Determines whether or not this system supports a universal time clock.
static int	modules() The set of modules supported.
static void	setMaximumConcurrentLocks(int max) setMaximumConcurrentLocks sets the maximum number of locks that may be used simultaneously.
static void	setMaximumConcurrentLocks(int max, boolean hard) setMaximumConcurrentLocks sets the maximum number of locks that may be used simultaneously.
static void	setSecurityManager(RealtimeSecurity manager) setSecurityManager replaces the current security manager by a new manager.
static boolean	supports(RTSJModule module) Determines whether or not a particular module is supported.

Methods inherited from class java.lang.Object

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

Field Detail

BIG_ENDIAN

@Deprecated
public static final byte BIG_ENDIAN

Deprecated. RTSJ 2.0

Value indicating that the highest order byte of a bit word is stored at the lowest byte address: the int 0x0A0B0C0D is stored in the byte sequence 0x0A, 0x0B, 0x0C, 0x0D. and the long 0x0102030405060708 is stored in the sequence 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08.

LITTLE_ENDIAN

@Deprecated
public static final byte LITTLE_ENDIAN

Deprecated. RTSJ 2.0

Value indicating that the lowest order byte of a word is stored at the lowest byte address: the int 0x0A0B0C0D is stored in the byte sequence 0x0D, 0x0C, 0x0B, 0x0A and the long 0x0102030405060708 is stored in the sequence 0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01.

BYTE_ORDER

@Deprecated
public static final byte BYTE_ORDER

Deprecated. RTSJ 2.0

Byte order of the current hardware of the system this is running on. This is either BIG_ENDIAN or LITTLE_ENDIAN.

Method Detail

currentGC

public static GarbageCollector currentGC()

currentGC returns the singleton instance of the garbage collector used by the system to recycle memory allocated in HeapMemory. For JamaicaVM, this is the garbage collector described in

Fridtjof Siebert, Hard Real-Time Garbage Collection in Modern Object Oriented Programming Languages, aicas GmbH, Karlsruhe, 2002, ISBN 3-8311-3893-1

Returns:

the current instance of the garbage collector.

getConcurrentLocksUsed

public static int getConcurrentLocksUsed()

getConcurrentLocksUsed returns the number of locks that have been used concurrently by the system. This may be used to tune the system on a call to setMaximumConcurrentLocks. If the system does not track this number, -1 is returned. JamaicaVM does not limit the maximum number of locks used concurrently, so it also does not track the number, this function always returns -1.

Returns:

the maximum number of lacks that were used concurrently, or -1 if this number is not known.

getMaximumConcurrentLocks

public static int getMaximumConcurrentLocks()

getMaximumConcurrentLocks returns the number of locks that may be used concurrently without requiring an extra overhead (for allocating an extra monitor object or similar).

For JamaicaVM, there is not restriction on the number of locks that may be used concurrently, and there is no extra overhead on the use of a lock since all required information is inlined. This function returns Integer.MAX_VALUE for JamaicaVM.

Returns:

the number of locks that can be used simultaneously by this implementation.

getSecurityManager

@Deprecated
public static RealtimeSecurity getSecurityManager()

Deprecated. RTSJ 2.0

getSecurityManager returns the current security manager instance.

Returns:

the current security manager.

setMaximumConcurrentLocks

public static void setMaximumConcurrentLocks(int max)

setMaximumConcurrentLocks sets the maximum number of locks that may be used simultaneously. This may be used by systems that require a preallocated set of locks for efficient monitor access.

In JamaicaVM, no allocation of specific memory of locks is required, this function has no effect in JamaicaVM.

Parameters:

max - The maximum number of locks.

setMaximumConcurrentLocks

public static void setMaximumConcurrentLocks(int max,
                                             boolean hard)

setMaximumConcurrentLocks sets the maximum number of locks that may be used simultaneously. This may be used by systems that require a preallocated set of locks for efficient monitor access.

In JamaicaVM, no allocation of specific memory of locks is required, this function has no effect in JamaicaVM.

Parameters:

max - The maximum number of locks.

hard - if this parameter is set, exceeding the number of permitted locks at runtime will cause a ResourceLimitError. On JamaicaVM, there is no such limit, so this parameter is ignored.

setSecurityManager

public static void setSecurityManager(RealtimeSecurity manager)

setSecurityManager replaces the current security manager by a new manager.

Throws:

IllegalArgumentException - if manger is null.

SecurityException - if the security manager has already been set.

Parameters:

manager - the new security manager.

getInitialMonitorControl

public static MonitorControl getInitialMonitorControl()

Get the monitor control object of the policy that is used during system startup.

Returns:

original monitor control policy.

Since:

RTSJ V1.0.1

supports

public static boolean supports(RTSJModule module)

Determines whether or not a particular module is supported.

Parameters:

module - The identifier of the module to be checked for support.

Returns:

true when module is supported; otherwise false.

Since:

RTSJ 2.0

modules

public static int modules()

The set of modules supported.

Returns:

an integer representing all the modules supported.

Since:

RTSJ 2.0

hasUniversalClock

public static boolean hasUniversalClock()

Determines whether or not this system supports a universal time clock.

Returns:

true when the system can provide a universal time clock.

canEnforceCost

public static boolean canEnforceCost()

Determines whether or not hard cost enforcement is supported.

Returns:

true when cost enforcement is supported; otherwise false.

Since:

RTSJ 2.0

canEnforceAllocationRate

public static boolean canEnforceAllocationRate()

Determines whether or not allocation rate enforcement is supported.

Returns:

true when allocation rate enforcement is supported, otherwise false.

Since:

RTSJ 2.0