net.uncontended.precipice.concurrent

Class LongMaxUpdater

java.lang.Object

java.lang.Number

net.uncontended.precipice.concurrent.LongMaxUpdater

All Implemented Interfaces:

java.io.Serializable

public class LongMaxUpdater
extends java.lang.Number
implements java.io.Serializable

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

This class extends Number, but does not define methods such as 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

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LongMaxUpdater() Creates a new instance with initial maximum of Long.MIN_VALUE.

Method Summary

Modifier and Type	Method and Description
double	doubleValue() Returns the max() as a double after a widening primitive conversion.
float	floatValue() Returns the max() as a float after a widening primitive conversion.
int	intValue() Returns the max() as an int after a narrowing primitive conversion.
long	longValue() Equivalent to max().
long	max() Returns the current maximum.
long	maxThenReset() Equivalent in effect to max() followed by reset().
void	reset() Resets variables maintaining updates to Long.MIN_VALUE.
java.lang.String	toString() Returns the String representation of the max().
void	update(long 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

LongMaxUpdater

public LongMaxUpdater()

Creates a new instance with initial maximum of Long.MIN_VALUE.

Method Detail

update

public void update(long x)

Updates the maximum to be at least the given value.

Parameters:

x - the value to update

max

public long 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 Long.MIN_VALUE. 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 long 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 java.lang.String toString()

Returns the String representation of the max().

Overrides:

toString in class java.lang.Object

Returns:

the String representation of the max()

longValue

public long longValue()

Equivalent to max().

Specified by:

longValue in class java.lang.Number

Returns:

the maximum

intValue

public int intValue()

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

Specified by:

intValue in class java.lang.Number

floatValue

public float floatValue()

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

Specified by:

floatValue in class java.lang.Number

doubleValue

public double doubleValue()

Returns the max() as a double after a widening primitive conversion.

Specified by:

doubleValue in class java.lang.Number