com.isti.util
Class ProgramSingleton

java.lang.Object
  com.isti.util.ProgramSingleton

public class ProgramSingleton

extends java.lang.Object

Class ProgramSingleton manages a "program singleton" file used to determine if another instance of the given program is already running. The name of the "program singleton" file will be the program name given to the constructor plus the extension ".psf". While the file-manager thread created by this class is running, the file will be written to once every 30 seconds. The standard usage of this class is to call the 'initialize()' method in the main method of the program (aborting if the method returns false) and call the 'close()' method from the shutdown-hook for the program (setup via 'Runtime.getRuntime().addShutdownHook()').

Nested Class Summary

protected class

ProgramSingleton.FileManagerThread Class FileManagerThread defines the "program singleton" file managing thread.

Field Summary

protected ProgramSingleton.FileManagerThread	fileManagerThreadObj
static java.lang.String	SINGLETON_FILE_EXT The singleton file extension.
protected java.io.RandomAccessFile	singletonFileAccessObj
protected java.io.File	singletonFileObj
protected int	UPDATE_INTERVAL_MS

Constructor Summary

ProgramSingleton(java.io.File singletonFileObj)
Creates a "program singleton" file manager.

ProgramSingleton(java.io.File parent, java.lang.String programNameStr)
Creates a "program singleton" file manager.

ProgramSingleton(java.lang.String programNameStr)
Creates a "program singleton" file manager.

ProgramSingleton(java.lang.String parent, java.lang.String programNameStr)
Creates a "program singleton" file manager.

Method Summary

void	close() Terminates the "program singleton" file manager thread and closes and deletes the "program singleton" file.
boolean	initialize() Checks to see if another instance of the program is running and, if not, initializes the "program singleton" file manager thread.
boolean	isRunning() Determines if another instance of the program is running or not.
boolean	waitForClose(int millis) Wait for the program close.
boolean	waitForClose(int millis, int retry) Wait for the program close.

Methods inherited from class java.lang.Object

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

Field Detail

SINGLETON_FILE_EXT

public static final java.lang.String SINGLETON_FILE_EXT

The singleton file extension.

See Also:

Constant Field Values

singletonFileObj

protected final java.io.File singletonFileObj

UPDATE_INTERVAL_MS

protected final int UPDATE_INTERVAL_MS

See Also:

Constant Field Values

fileManagerThreadObj

protected ProgramSingleton.FileManagerThread fileManagerThreadObj

singletonFileAccessObj

protected java.io.RandomAccessFile singletonFileAccessObj

Constructor Detail

ProgramSingleton

public ProgramSingleton(java.lang.String programNameStr)

Creates a "program singleton" file manager.

Parameters:

programNameStr - the program name to be used.

ProgramSingleton

public ProgramSingleton(java.lang.String parent,
                        java.lang.String programNameStr)

Creates a "program singleton" file manager.

Parameters:

parent - the parent pathname string.

programNameStr - the program name to be used.

ProgramSingleton

public ProgramSingleton(java.io.File parent,
                        java.lang.String programNameStr)

Creates a "program singleton" file manager.

Parameters:

parent - the parent file.

programNameStr - the program name to be used.

ProgramSingleton

public ProgramSingleton(java.io.File singletonFileObj)

Creates a "program singleton" file manager.

Parameters:

singletonFileObj - the singleton file object.

Method Detail

isRunning

public boolean isRunning()

Determines if another instance of the program is running or not.

Returns:

true if another instance is running, false otherwise.

initialize

public boolean initialize()

Checks to see if another instance of the program is running and, if not, initializes the "program singleton" file manager thread.

Returns:

true if successful, false if another instance of the program is already running.

close

public void close()

Terminates the "program singleton" file manager thread and closes and deletes the "program singleton" file.

waitForClose

public boolean waitForClose(int millis)

Wait for the program close.

Parameters:

millis - Waits at most millis milliseconds for this program to close. A timeout of 0 means to wait forever.

Returns:

true if the program closed, false otherwise.

waitForClose

public boolean waitForClose(int millis,
                            int retry)

Wait for the program close.

Parameters:

millis - Waits at most millis milliseconds for this program to close. A timeout of 0 means to wait forever.

retry - the number of millis to wait between retries.

Returns:

true if the program closed, false otherwise.