We also save the previous position of a rectangle before moving it into a Memento in Java

Drawer PDF-417 2d barcode in Java We also save the previous position of a rectangle before moving it into a Memento
We also save the previous position of a rectangle before moving it into a Memento
PDF-417 2d Barcode Generation In Java
Using Barcode maker for Java Control to generate, create PDF-417 2d barcode image in Java applications.
public void rememberPosition() { if (rectSelected) { Memento m = new Memento (selectedRectangle); caretakeraddElement(m); repaint(); } }
Generate Barcode In Java
Using Barcode encoder for Java Control to generate, create barcode image in Java applications.
The undo method simply decides whether to reduce the drawing list by one or to invoke the restore method of a Memento
Recognizing Barcode In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
public void undo() { if (undoListsize() > 0) { //get the last element in the undo list Object obj = undoListlastElement(); undoListremoveElement(obj); //and remove it if (obj instanceof Integer) remove ((Integer)obj); //remove the integer or], //Memento
PDF417 Encoder In C#
Using Barcode creation for Visual Studio .NET Control to generate, create PDF417 image in .NET applications.
else remove((Memento)obj); } }
Generate PDF417 In Visual Studio .NET
Using Barcode generator for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
The complete class structure is diagrammed in Figure 214 Figure 214 The class structure for the drawing program using the Memento pattern
PDF 417 Creation In VS .NET
Using Barcode generation for .NET Control to generate, create PDF-417 2d barcode image in .NET applications.
Consequences of the Memento Pattern
Print PDF417 In Visual Basic .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create PDF-417 2d barcode image in .NET applications.
1 The Memento pattern provides a way to preserve the state of an object while preserving encapsulation, in languages where this is possible Thus data that only the Originator class should have access to effectively remain private The pattern also preserves the simplicity of the Originator class by delegating the saving and restoring of information to the Memento class 2 However, the amount of data that a Memento must save might be quite large, thus taking up a fair amount of storage This also affects the Caretaker class (here, the Mediator), which might have to design strategies to limit the number of objects for which it saves state In the example in this chapter, we imposed no such limits When objects change in a predictable manner, each Memento might be able to get by with saving only incremental changes of an object's state
DataMatrix Creator In Java
Using Barcode creator for Java Control to generate, create DataMatrix image in Java applications.
lightbulb Thought Question
EAN 128 Generator In Java
Using Barcode generator for Java Control to generate, create GS1 128 image in Java applications.
1 The Memento pattern can be used to restore an object's state when a process fails If a database update fails because of a dropped network connection, you should be able to restore the data in your cached data to their previous state Rewrite the Database class in the Fa ade pattern ( 13) to allow for such failures
Encoding Barcode In Java
Using Barcode creator for Java Control to generate, create bar code image in Java applications.
Programs on the CD-ROM
Code 3 Of 9 Printer In Java
Using Barcode maker for Java Control to generate, create Code 3/9 image in Java applications.
Description Allows you to draw and move rectangles and undo these \Memento\MemDrawjava operations
UPC A Creator In Java
Using Barcode maker for Java Control to generate, create UPC-A image in Java applications.
Programs
OneCode Drawer In Java
Using Barcode maker for Java Control to generate, create OneCode image in Java applications.
22 The Observer Pattern
Making Barcode In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create bar code image in ASP.NET applications.
In this chapter we discuss how you can use the Observer pattern to present data in several forms at once In the more sophisticated windowing world, we often want to display data in more than one form at the same time and have all of the displays reflect any changes in the data For example, we might represent stock price changes as both a graph and a table or list box Each time the price changes, we'd expect both representations to change at once without any action on our part We expect this sort of behavior because many Windows applications, such as Excel, demonstrate such behavior However, nothing inherent in Windows allows this activity, and, as you might know, programming directly in Windows in C or C++ is quite complicated In Java, however, you can easily use the Observer pattern to cause your program to behave in this way The Observer pattern assumes that the object containing the data is separate from the objects that display the data and that these data objects observe changes in those data This idea is illustrated in Figure 221 Figure 221 Data are displayed as a list and in some graphical mode
Scan USS Code 39 In Visual Studio .NET
Using Barcode decoder for .NET Control to read, scan read, scan image in .NET framework applications.
When we implement the Observer pattern, we usually refer to the data as the Subject and each of the displays as Observers Each Observer registers its interest in the data by calling a public method in the Subject, and each has a known interface that the Subject calls when the data change We could define these interfaces as follows:
Painting Data Matrix ECC200 In Visual Studio .NET
Using Barcode encoder for ASP.NET Control to generate, create Data Matrix ECC200 image in ASP.NET applications.
public interface Observer { //notify Observers that a change has taken place public void sendNotify(String s); } public interface Subject {
Data Matrix 2d Barcode Decoder In .NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET framework applications.
//tell the Subject that you are interested in changes public void registerInterest(Observer obs); }
UCC - 12 Printer In VS .NET
Using Barcode maker for ASP.NET Control to generate, create GS1 128 image in ASP.NET applications.
The advantages of defining these abstract interfaces are that you can write any sort of class objects you want as long as they implement these interfaces, and that you can declare these objects to be of type Subject and Observer no matter what else they do
Printing EAN-13 In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create EAN 13 image in ASP.NET applications.
Creating Barcode In Visual C#
Using Barcode generation for VS .NET Control to generate, create barcode image in .NET framework applications.