Clock

java.lang.Object
- javax.safetycritical.Clock

```
@SCJAllowed
public abstract class Clock
extends java.lang.Object
```
A clock marks the passing of time. It has a concept of now that can be queried through Clock.getTime().
The Clock instance returned by getRealtimeClock() may be used in any context that requires a clock.
Version:

1.0; - May 2012

Author:

Anders P. Ravn, Aalborg University, apr@cs.aau.dk,
Hans Søndergaard, VIA University College, Denmark, hso@viauc.dk

Relative_to_SCJ_Draft_Version_0.79:
- SCJ issue: User defined clocks?
- SCJ issue: Is the clock implementing an event queues - i.e. implementing an AsyncEvent ?
When a clock drives events, it implements a periodic handler. If a mix of an aperiodic and a periodic handler is essential, a unification at the level of aperiodic event handler seems more general. I.e. set periods for aperiodic event handlers.
- SCJ issue: The semantics of getTime with dest differs from getTime with no arguments. It is made consistent below.
- semantic issue: EpochOffSet must be relative to RealTimeClock?
- implementation issue: The constructor public Clock() is public, if user-defined clocks are allowed, else package protected.
- implementation issue: Omitted ? , - the following methods are not implemented:
- public abstract boolean resetTargetTime(AbsoluteTime time);

Constructor Summary

Constructors
Constructor and Description

Clock()
This constructor for the abstract class may allocate objects within the same MemoryArea that holds the implicit this argument.

Constructors
Constructor and Description
`Clock()` This constructor for the abstract class may allocate objects within the same `MemoryArea` that holds the implicit this argument.

Method Summary

Methods
Modifier and Type	Method and Description
`abstract boolean`	`drivesEvents()`
`abstract RelativeTime`	`getEpochOffset()` Returns the relative time of the offset of the epoch of this clock from the Epoch of the `RealtimeClock`.
`static Clock`	`getRealtimeClock()`
`abstract RelativeTime`	`getResolution()` Gets the resolution of the clock, the nominal interval between ticks.
`abstract RelativeTime`	`getResolution(RelativeTime dest)` Gets the resolution of the clock, the nominal interval between ticks and stores the result in `dest`.
`abstract AbsoluteTime`	`getTime()` Creates a new object representing now of this clock.
`abstract AbsoluteTime`	`getTime(AbsoluteTime dest)` Stores now of this clock in `dest`.
`abstract void`	`registerCallBack(AbsoluteTime t, ClockCallBack clockEvent)`
`abstract boolean`	`resetTargetTime(AbsoluteTime time)`

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Clock
```
public Clock()
```
    This constructor for the abstract class may allocate objects within the same MemoryArea that holds the implicit this argument. Allocates resolution here.
- Method Detail
  - getRealtimeClock
```
public static Clock getRealtimeClock()
```
    Returns:
    The singleton instance of the default Clock.
  - getTime
```
@SCJAllowed
public abstract AbsoluteTime getTime()
```
    Creates a new object representing now of this clock.
    
    Returns:
    A new AbsoluteTime object whose time is now of this clock.
  - getTime
```
@SCJAllowed
public abstract AbsoluteTime getTime(AbsoluteTime dest)
```
    Stores now of this clock in dest.
    
    Parameters:
    dest - If destis null, allocate a new AbsoluteTime instance to hold the returned value.
    
    Returns:
    The resulting dest value.
  - getResolution
```
@SCJAllowed
public abstract RelativeTime getResolution()
```
    Gets the resolution of the clock, the nominal interval between ticks.
    
    Returns:
    The initially allocated resolution object.
  - getEpochOffset
```
@SCJAllowed
public abstract RelativeTime getEpochOffset()
```
    Returns the relative time of the offset of the epoch of this clock from the Epoch of the RealtimeClock.
    
    Returns:
    The offset of this clock epoch from the RealtimeClock.
  - getResolution
```
@SCJAllowed
public abstract RelativeTime getResolution(RelativeTime dest)
```
    Gets the resolution of the clock, the nominal interval between ticks and stores the result in dest.
    
    Parameters:
    dest - If dest is null, allocate a new RelativeTime instance to hold the returned value.
    
    Returns:
    The resulting dest value.
  - drivesEvents
```
@SCJAllowed
public abstract boolean drivesEvents()
```
    Relative_to_SCJ_Draft_Version_0.79:
    
    Omitted?, - not implemented
  - registerCallBack
```
@SCJAllowed(value=LEVEL_1)
public abstract void registerCallBack(AbsoluteTime t,
                                           ClockCallBack clockEvent)
```
    Relative_to_SCJ_Draft_Version_0.79:
    
    Omitted?, - not implemented
  - resetTargetTime
```
@SCJAllowed(value=LEVEL_1)
public abstract boolean resetTargetTime(AbsoluteTime time)
```
    Relative_to_SCJ_Draft_Version_0.79:
    
    Omitted?, - not implemented

Class Clock

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Clock

Method Detail

getRealtimeClock

getTime

getTime

getResolution

getEpochOffset

getResolution

drivesEvents

registerCallBack

resetTargetTime