com.programix.thread
Class Counter

java.lang.Object
  com.programix.thread.Counter

All Implemented Interfaces:

ThreadSafe

public class Counter
extends Object
implements ThreadSafe

This class serves as a thread-safe integer counter. In fact, there's no requirement that the value only increment or decrement—the value can hop around to any value by using setCount(int).

Author:

Paul Hyde

Constructor Summary

Counter()
Creates a counter that starts off with a value of 0.

Counter(int initialCount)
Creates a counter that starts off with the specified initialCount.

Counter(int initialCount, Object lockObject)
Creates a counter that starts off with the specified initialCount.

Counter(int initialCount, Waiter waiter)
Creates a counter that starts off with the specified initialCount.

Counter(Object lockObject)
Creates a counter that starts off with a value of 0.

Method Summary

Waiter.Condition	createAtLeastCondition(int minCount) Returns a Waiter.Condition that can be used to wait while or wait until the count is greater than or equal to the specified minCount.
Waiter.Condition	createAtMostCondition(int maxCount) Returns a Waiter.Condition that can be used to wait while or wait until the count is less than or equal to the specified maxCount.
Waiter.Condition	createCondition(Waiter.Expression expression) Returns a Waiter.Condition that can be used to wait while or wait until the the specified expression is true.
Waiter.Condition	createRangeCondition(int min, int max) Returns a Waiter.Condition that can be used to wait while or wait until the count is within the specified range (inclusive of the min and max).
void	decrement()
boolean	decrementIfNotShutdown() Potentially decrements the counter returning true if the counter was decremented or false is the counter was not changed because it's already been shutdown.
int	getCount()
Object	getLockObject()
Waiter	getWaiter()
void	increment()
boolean	incrementIfNotShutdown() Potentially increments the counter returning true if the counter was incremented or false is the counter was not changed because it's already been shutdown.
boolean	isNotZero()
boolean	isShutdown()
boolean	isZero()
void	setCount(int newCount)
void	shutdown() Called to shutdown all access to this counter and to dislodge any threads waiting on conditions.
void	waitUntilNegative() Waits until the count is a negative number (less than zero).
void	waitUntilNegative(long msTimeout) Waits until the count is a negative number (less than zero).
void	waitUntilPositive() Waits until the count is a positive number (greater than zero).
void	waitUntilPositive(long msTimeout) Waits until the count is a positive number (greater than zero).
void	waitUntilZero() Waits until the count is exactly zero.
void	waitUntilZero(long msTimeout) Waits until the count is exactly zero.
void	waitWhileNegative() Waits while the count is a negative number (less than zero).
void	waitWhileNegative(long msTimeout) Waits while the count is a negative number (less than zero).
void	waitWhilePositive() Waits while the count is a positive number (greater than zero).
void	waitWhilePositive(long msTimeout) Waits while the count is a positive number (greater than zero).
void	waitWhileZero() Waits while the count is exactly zero.
void	waitWhileZero(long msTimeout) Waits while the count is exactly zero.

Methods inherited from class java.lang.Object

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

Constructor Detail

Counter

public Counter(int initialCount,
               Waiter waiter)

Creates a counter that starts off with the specified initialCount.

Parameters:

initialCount - the starting value.

waiter - the Waiter to use. If null, then a new Waiter is automatically created.

Counter

public Counter(int initialCount,
               Object lockObject)

Creates a counter that starts off with the specified initialCount.

Parameters:

initialCount - the starting value.

lockObject - the object to synchronize on. If null, the the synchronization will be on this instance.

Counter

public Counter(int initialCount)

Creates a counter that starts off with the specified initialCount.

Parameters:

initialCount - the starting value.

Counter

public Counter(Object lockObject)

Creates a counter that starts off with a value of 0.

Parameters:

lockObject - the object to synchronize on. If null, the the synchronization will be on this instance.

Counter

public Counter()

Creates a counter that starts off with a value of 0.

Method Detail

getCount

public int getCount()
             throws ShutdownException

Throws:

ShutdownException

setCount

public void setCount(int newCount)
              throws ShutdownException

Throws:

ShutdownException

increment

public void increment()
               throws ShutdownException

Throws:

ShutdownException

incrementIfNotShutdown

public boolean incrementIfNotShutdown()

Potentially increments the counter returning true if the counter was incremented or false is the counter was not changed because it's already been shutdown.

decrement

public void decrement()
               throws ShutdownException

Throws:

ShutdownException

decrementIfNotShutdown

public boolean decrementIfNotShutdown()

Potentially decrements the counter returning true if the counter was decremented or false is the counter was not changed because it's already been shutdown.

isZero

public boolean isZero()
               throws ShutdownException

Throws:

ShutdownException

isNotZero

public boolean isNotZero()
                  throws ShutdownException

Throws:

ShutdownException

waitWhileZero

public void waitWhileZero(long msTimeout)
                   throws TimedOutException,
                          ShutdownException,
                          InterruptException

Waits while the count is exactly zero.

Throws:

TimedOutException

ShutdownException

InterruptException

waitWhileZero

public void waitWhileZero()
                   throws ShutdownException,
                          InterruptException

Waits while the count is exactly zero.

Throws:

ShutdownException

InterruptException

waitUntilZero

public void waitUntilZero(long msTimeout)
                   throws TimedOutException,
                          ShutdownException,
                          InterruptException

Waits until the count is exactly zero.

Throws:

TimedOutException

ShutdownException

InterruptException

waitUntilZero

public void waitUntilZero()
                   throws ShutdownException,
                          InterruptException

Waits until the count is exactly zero.

Throws:

ShutdownException

InterruptException

waitWhilePositive

public void waitWhilePositive(long msTimeout)
                       throws TimedOutException,
                              ShutdownException,
                              InterruptException

Waits while the count is a positive number (greater than zero).

Throws:

TimedOutException

ShutdownException

InterruptException

waitWhilePositive

public void waitWhilePositive()
                       throws ShutdownException,
                              InterruptException

Waits while the count is a positive number (greater than zero).

Throws:

ShutdownException

InterruptException

waitUntilPositive

public void waitUntilPositive(long msTimeout)
                       throws TimedOutException,
                              ShutdownException,
                              InterruptException

Waits until the count is a positive number (greater than zero).

Throws:

TimedOutException

ShutdownException

InterruptException

waitUntilPositive

public void waitUntilPositive()
                       throws ShutdownException,
                              InterruptException

Waits until the count is a positive number (greater than zero).

Throws:

ShutdownException

InterruptException

waitWhileNegative

public void waitWhileNegative(long msTimeout)
                       throws TimedOutException,
                              ShutdownException,
                              InterruptException

Waits while the count is a negative number (less than zero).

Throws:

TimedOutException

ShutdownException

InterruptException

waitWhileNegative

public void waitWhileNegative()
                       throws ShutdownException,
                              InterruptException

Waits while the count is a negative number (less than zero).

Throws:

ShutdownException

InterruptException

waitUntilNegative

public void waitUntilNegative(long msTimeout)
                       throws TimedOutException,
                              ShutdownException,
                              InterruptException

Waits until the count is a negative number (less than zero).

Throws:

TimedOutException

ShutdownException

InterruptException

waitUntilNegative

public void waitUntilNegative()
                       throws ShutdownException,
                              InterruptException

Waits until the count is a negative number (less than zero).

Throws:

ShutdownException

InterruptException

createAtLeastCondition

public Waiter.Condition createAtLeastCondition(int minCount)

Returns a Waiter.Condition that can be used to wait while or wait until the count is greater than or equal to the specified minCount.

createAtMostCondition

public Waiter.Condition createAtMostCondition(int maxCount)

Returns a Waiter.Condition that can be used to wait while or wait until the count is less than or equal to the specified maxCount.

createRangeCondition

public Waiter.Condition createRangeCondition(int min,
                                             int max)

Returns a Waiter.Condition that can be used to wait while or wait until the count is within the specified range (inclusive of the min and max).

createCondition

public Waiter.Condition createCondition(Waiter.Expression expression)

Returns a Waiter.Condition that can be used to wait while or wait until the the specified expression is true.

getWaiter

public Waiter getWaiter()

shutdown

public void shutdown()

Called to shutdown all access to this counter and to dislodge any threads waiting on conditions.

isShutdown

public boolean isShutdown()

getLockObject

public Object getLockObject()