com.qualcomm.robotcore.util

Class LastKnown<T>

java.lang.Object

com.qualcomm.robotcore.util.LastKnown<T>

public class LastKnown<T>
extends java.lang.Object

Instances of LastKnown can keep track of a last known value for a certain datum, together with whether in fact any such last value is known at all. Values can become unknown either due to explicit invalidation, or by not being fresh enough. The requirement that values be 'fresh' helps guard against an error situation in which the underlying setting has actually been lost and the user's code is simply trying to apply it. Were we to not have this, such error situations might never be repaired. This class is NOT thread-safe.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	isValid
protected double	msFreshness
protected ElapsedTime	timer
protected T	value

Constructor Summary

Constructors

Constructor and Description
LastKnown()
LastKnown(double msFreshness)

Method Summary

Modifier and Type	Method and Description
static <X> LastKnown<X>[]	createArray(int length)
T	getNonTimedValue() Returns the stored value, w/o using a timer to invalidate
T	getRawValue() Returns the stored value, whether or not it is valid
T	getValue() Returns the last known value, or null if not valid
void	invalidate() Marks the last known value as invalid.
static <X> void	invalidateArray(LastKnown<X>[] array)
boolean	isValid() Returns whether a last value is currently known and is fresh enough.
boolean	isValue(T valueQ) Answers whether the last known value is both valid and equal to the value indicated.
T	setValue(T value) If non-null, sets the current value to be the indicated (known) value and resets the freshness timer.
boolean	updateValue(T valueQ) If the last known value is not both valid and equal to the indicated value, updates it to be same and returns true; otherwise, returns false.

Methods inherited from class java.lang.Object

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

Field Detail

value

protected T value

isValid

protected boolean isValid

timer

protected ElapsedTime timer

msFreshness

protected double msFreshness

Constructor Detail

LastKnown

public LastKnown()

LastKnown

public LastKnown(double msFreshness)

Method Detail

createArray

public static <X> LastKnown<X>[] createArray(int length)

invalidateArray

public static <X> void invalidateArray(LastKnown<X>[] array)

invalidate

public void invalidate()

Marks the last known value as invalid. However, the value internally stored is uneffected.

See Also:

getRawValue(), getValue()

isValid

public boolean isValid()

Returns whether a last value is currently known and is fresh enough. Note that a value which is valid may spontaneously become invalid (because it expires) but a value which is invalid will never spontaneously become valid.

Returns:

whether a last value is currently known and is fresh enough

getValue

public T getValue()

Returns the last known value, or null if not valid

Returns:

the last known value

getNonTimedValue

public T getNonTimedValue()

Returns the stored value, w/o using a timer to invalidate

Returns:

the raw stored value.

getRawValue

public T getRawValue()

Returns the stored value, whether or not it is valid

Returns:

the raw stored value.

setValue

public T setValue(T value)

If non-null, sets the current value to be the indicated (known) value and resets the freshness timer. If null, this is equivalent to invalidate().

Returns:

the previous value.

isValue

public boolean isValue(T valueQ)

Answers whether the last known value is both valid and equal to the value indicated. Note that the .equals() method is used to make the comparison.

Parameters:

valueQ - the value queried

Returns:

whether the last known value is both valid and equal to the value indicated

updateValue

public boolean updateValue(T valueQ)

If the last known value is not both valid and equal to the indicated value, updates it to be same and returns true; otherwise, returns false.

Parameters:

valueQ - the value queried

Returns:

whether the value was just updated