y.base
Class CommandStream

java.lang.Object
  |
  +--y.base.CommandStream

public class CommandStream

extends Object

This class represents a stream of Commands. It is useful for implementing undoable operations in applications.

Constructor Summary

CommandStream()
Initializes a new CommandStream object with unlimited size

Method Summary

Command	backward() Returns the next command for which an undo operation is meaningful and consistent in respect to the order of the commands registered.
boolean	backwardPossible() Returns true iff it is possible to retrive a command by calling backward().
void	clear() Clears this stream
void	clearTo(Command com) Clears the stream up to the given command (exclusive)
Command	forward() Returns the next command for which a redo operation is meaningful and consistent in respect to the order of the commands registered.
boolean	forwardPossible() Returns true iff it is possible to retrive a command by calling forward().
Object	getActiveToken() Obtains a token which determines the currently active position in the stream.
int	getMaximumSize() Returns the maximum size of this stream
boolean	isActiveToken(Object token) determines, whether the stream is currently at the same position, the time the token was obtained using CommandStream.getActiveToken()
void	push(Command com) Addes the given command to this stream
void	setMaximumSize(int maxSize) Sets the maximum size of this stream

Methods inherited from class java.lang.Object

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

Constructor Detail

CommandStream

public CommandStream()

Initializes a new CommandStream object with unlimited size

Method Detail

setMaximumSize

public void setMaximumSize(int maxSize)

Sets the maximum size of this stream

getMaximumSize

public int getMaximumSize()

Returns the maximum size of this stream

push

public void push(Command com)

Addes the given command to this stream

backwardPossible

public boolean backwardPossible()

Returns true iff it is possible to retrive a command by calling backward().

clearTo

public void clearTo(Command com)

Clears the stream up to the given command (exclusive)

clear

public void clear()

Clears this stream

backward

public Command backward()

Returns the next command for which an undo operation is meaningful and consistent in respect to the order of the commands registered. If no such command exists null is returned.

forwardPossible

public boolean forwardPossible()

Returns true iff it is possible to retrive a command by calling forward().

forward

public Command forward()

Returns the next command for which a redo operation is meaningful and consistent in respect to the order of the commands registered. If no such command exists null is returned.

getActiveToken

public Object getActiveToken()

Obtains a token which determines the currently active position in the stream. CommandStream.isActiveToken(Object) can be used to determine, whether the current stream position equals the position at the time to token was obtained

Returns:

a token

isActiveToken

public boolean isActiveToken(Object token)

determines, whether the stream is currently at the same position, the time the token was obtained using CommandStream.getActiveToken()

Parameters:

token - the token

Returns:

true if the stream is at the same position