jsr166e

Class DoubleMaxUpdater

java.lang.Object

java.lang.Number

jsr166e.DoubleMaxUpdater

All Implemented Interfaces:

Serializable

public class DoubleMaxUpdater
extends Number
implements Serializable

One or more variables that together maintain a running double maximum with initial value Double.NEGATIVE_INFINITY. When updates (method update(double)) are contended across threads, the set of variables may grow dynamically to reduce contention. Method max() (or, equivalently, doubleValue()) returns the current maximum across the variables maintaining updates.

This class extends Number, but does not define methods such as equals, hashCode and compareTo because instances are expected to be mutated, and so are not useful as collection keys.

jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic.

Since:

1.8

Author:

Doug Lea

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
DoubleMaxUpdater() Creates a new instance with initial value of Double.NEGATIVE_INFINITY.

Method Summary

Methods

Modifier and Type	Method and Description
double	doubleValue() Equivalent to max().
float	floatValue() Returns the max() as a float after a narrowing primitive conversion.
int	intValue() Returns the max() as an int after a narrowing primitive conversion.
long	longValue() Returns the max() as a long after a narrowing primitive conversion.
double	max() Returns the current maximum.
double	maxThenReset() Equivalent in effect to max() followed by reset().
void	reset() Resets variables maintaining updates to Double.NEGATIVE_INFINITY.
String	toString() Returns the String representation of the max().
void	update(double x) Updates the maximum to be at least the given value.

Methods inherited from class java.lang.Number

byteValue, shortValue

Methods inherited from class java.lang.Object

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

Constructor Detail

DoubleMaxUpdater

public DoubleMaxUpdater()

Creates a new instance with initial value of Double.NEGATIVE_INFINITY.

Method Detail

update

public void update(double x)

Updates the maximum to be at least the given value.

Parameters:

x - the value to update

max

public double max()

Returns the current maximum. The returned value is NOT an atomic snapshot; invocation in the absence of concurrent updates returns an accurate result, but concurrent updates that occur while the value is being calculated might not be incorporated.

Returns:

the maximum

reset

public void reset()

Resets variables maintaining updates to Double.NEGATIVE_INFINITY. This method may be a useful alternative to creating a new updater, but is only effective if there are no concurrent updates. Because this method is intrinsically racy, it should only be used when it is known that no threads are concurrently updating.

maxThenReset

public double maxThenReset()

Equivalent in effect to max() followed by reset(). This method may apply for example during quiescent points between multithreaded computations. If there are updates concurrent with this method, the returned value is not guaranteed to be the final value occurring before the reset.

Returns:

the maximum

toString

public String toString()

Returns the String representation of the max().

Overrides:

toString in class Object

Returns:

the String representation of the max()

doubleValue

public double doubleValue()

Equivalent to max().

Specified by:

doubleValue in class Number

Returns:

the max

longValue

public long longValue()

Returns the max() as a long after a narrowing primitive conversion.

Specified by:

longValue in class Number

intValue

public int intValue()

Returns the max() as an int after a narrowing primitive conversion.

Specified by:

intValue in class Number

floatValue

public float floatValue()

Returns the max() as a float after a narrowing primitive conversion.

Specified by:

floatValue in class Number