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Explain, in detail and in writing, how the getExitString method shown in Figure 78 works. in .NET Produce Data Matrix in .NET Explain, in detail and in writing, how the getExitString method shown in Figure 78 works.

Explain, in detail and in writing, how the getExitString method shown in Figure 78 works. using barcode generating for visual studio .net control to generate, create ecc200 image in visual studio .net applications. Microsoft Windows Official Website Our goal to reduce coupling d VS .NET Data Matrix barcode emands that, as far as possible, changes to the Room class do not require changes to the Game class. We can still improve this.

Currently, we have still encoded in the Game class the knowledge that the information we want from a room consists of a description string and the exit string:. System.out.println("You are " + currentRoom.

getDescription()); System.out.println(currentRoom.

getExitString());. What if we add items to rooms .net vs 2010 Data Matrix ECC200 in our game Or monsters Or other players When we describe what we see, the list of items, monsters and other players should be included in the description of the room. We would not only need to make changes to the Room class to add these things, but also change the code segment above where the description is printed out.

This is again a breach of the responsibility-driven design rule. Since the Room class holds information about a room, it should also produce a description for a room. We can improve this by adding to the Room class the following method:.

/** * Return a long descripti on of this room, on the form: * You are in the kitchen. * Exits: north west */ public String getLongDescription() { return "You are " + description + ".\n" + getExitString(); }.

In the Game class, we then write System.out.println(currentRoo m.

getLongDescription());. The long description of a r gs1 datamatrix barcode for .NET oom now includes the description string, information about the exits, and may in the future include anything else there is to say about a room. When we make these future extensions, we will have to make changes to only a single class: the Room class.

Exercises: 7-12 7-13 7-14 Implement the changes described in this section in your own zuul project. Draw an object diagram with all objects in your game, the way they are just after starting the game. How does the object diagram change when you execute a go command .

7.8 Localizing change [concept box: localizing chan Data Matrix barcode for .NET ge] Another aspect of the de-coupling and responsibility principles is that of localizing change. We aim to create a class design that makes later changes easy by localizing the effects of a change.

Ideally, only a single class needs to be changed to make a modification. Sometimes several classes need change, but then we aim at this being as few classes as possible. In addition, the changes needed in other classes should be obvious, easy to detect, and easy to carry out.

To a large extent, we can achieve this by following good design rules such as using responsibility-driven design and aiming for loose coupling and high cohesion. In addition, however, we should have modification and extension in mind when we create our applications. It is important to anticipate that an aspect of our program might change, in order to make this change easy.

. 7.9 Implicit coupling We have seen that the use of visual .net Data Matrix barcode public fields is one practice that is likely to create an unnecessarily tight form of coupling between classes. With this tight coupling, it may be necessary to make changes to more than one class for what should have been a simple modification.

Therefore, public fields should be avoided. However, there are even worse forms of coupling: implicit coupling. Implicit coupling is a situation where one class depends on internal information of another, but this dependency is not immediately obvious.

The tight coupling in the case of the public fields was not good, but at least it was obvious: if we change the public fields in one class, and forget about the other, the application will not compile any more and the compiler will point out the problem. In cases of implicit coupling, omitting a necessary change can go undetected. We can see the problem arising if we try to add further command words to the game.

Suppose that we want to add the command look to the set of legal commands. The purpose of look is merely to print out the description of the room and the exits again (we look around the room ) this could be helpful if we have entered a sequence of commands in a room so that the description has scrolled out of view, and we cannot remember where the exits of the current room are. We can add a command word by simply adding it to the array of known words in the validCommands array in the CommandWords class:.

// a constant array that hold s all valid command words private static final String validCommands[] = { "go", "quit", "help", "look" };. This, by the way, shows an ex 2d Data Matrix barcode for .NET ample of good cohesion: Instead of defining the command words in the parser, which would have been one obvious possibility, the author created a separate class just to define the command words. This makes it now very easy for us to find the place where command words are defined, and it is easy to 205.

add one. The author was obvio usly thinking ahead, assuming that more commands may be added later, and created a structure that makes this very easy. We can test this already.

However, after making this change, when we execute the game and type the command look, nothing happens. This contrasts with the behavior of an unknown command word: if we type any unknown word, we see the reply.
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