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how can i implement Java class that emulates
some of the capabilities of old terminals. Our terminal has a display (basically, a
2-D array of characters), various buttons, and a way to dump its data to a file or to the
screen.
please can someone give me some hints please i really need them its my assignment m its due in few hours n i have been trying for days to do it but i couldn't
Can you explain the capabilities you want to emulate?
A text area would give you a 2D area to display on and allow input to be read.
the problem is im reading the assighment and im not understanding what i need to emulate
these are some of the things that i need to have in my code hopefuly they will help ... it may seem easy to you and clear but im really bad in programming and i need to pass this course so please help
The Button Interface
Think of a Button as a button on the keyboard. What can you do with a keyboard button?
For starters, you can press a button. So, let’s create the following interface:
package auk.csis130;
public interface Button {
public void press();
}
The Terminal Class
Fields and constructor: Our terminal emulator has (1) a two-dimensional array of
characters that holds the content of the display, and (2) a cursor which moves around the
screen when various keys are pressed. The constructor of the Terminal takes nothing,
and initializes the display array and cursor position. The display array must be a 16-
row by 32-column array of characters that initially contains the following text exactly:
1
2 *** SOUTHWEST TECHNICAL ***
3
4 CT-1024
5
6 TERMINAL SYSTEM
7
8 LETS YOU SEE UP TO SIXTEEN LINES
9 WITH UP TO THIRTY TWO CHARACTERS
10 ON ANY TELEVISION SCREEN -------
11 1024 CHARACTERS OF MEMORY ON TWO
12 PAGES. STANDARD EQUIPMENT ******
13
14
15 _
16
The constructor initializes the cursor position so that it is at row:15 column:14 of the
display. (If you use 0-based indices in your code, you should use row index 14 and
column index 13.)
2
Inspection: The method charAt takes two integers (row and col) and returns the character
displayed at that location. The row value is between 1 and 16 inclusive and the col
value is between 1 and 32 inclusive.
Dumping to an output device: The method dump takes one argument of type OutputStream
and prints the content of the display array to that output stream. So, the
output of this method should contain exactly 16 lines and each line should have exactly
32 characters, regardless of the content of each line or whether things were written to it
or not.
4 The Keyboard Keys
The terminal’s keyboard has many keys. We mentioned in Section 2, we will use objects
that implement the Button interface to represent these keys. These keys fall into many
categories, and therefore, each will be implemented using a class that does something
slightly different in its press() method. For example, the “Home” button causes the
cursor to go to the topmost leftmost position, so, the following code will create a terminal,
get the home button, and press it, to cause the terminal cursor to go to the home
position.
Terminal t = new Terminal();
Button clearBtn = t.getClearButton();
clearBtn.press(); // clears the screen
Button homeBtn = t.getHomeButton();
homeBtn.press(); // moves the cursor to the topleft corner
t.getCharButton(’a’).press(); // writes ’a’ and advances the cursor
t.dump(System.out); // shows a screen containing just ’a’
There are many different kinds of buttons and a corresponding set of methods that return
these buttons. The methods are summarized below.
• getClearButton(): Returns a Button that clears the entire display array. To clear
the array, it is sufficient to place a space character in every cell in the array.
• getHomeButton(): Returns a Button that moves the cursor to the top-left corner
of the display. It does not change the content of the display array.
• getCarriageReturnButton(): Returns a Button that moves the cursor to the beginning
of the same line.
• getLineFeedButton(): Returns a Button that moves the cursor to the next line
without changing the column. If the cursor is already in the last line, pressing
linefeed scrolls the display one line upwards. This causes the first line to be lost,
the second line to become the first, etc., etc., until the 16th line to become the 15th,
and creates a new and empty 16th line.
• getCharButton(char x): Takes a character and returns a Button that if pressed,
it types the given character x at the current cursor position (overwriting whatever
was there) and advances the cursor to the right. If the cursor is already at the last
column, it stays in the same place.
3
• getButton(ArrowDirection d): Takes a Direction d which may be one of UP,
DOWN, LEFT, or RIGHT and returns a Button that moves the cursor in the given direction.
If the cursor tries to move off the screen, it stays in the same place without
scrolling or wrapping. The ArrowDirection must be an enum written inside
the Terminal class. To refer to it from outside the class, you need to say Terminal.
ArrowDirection.
The only thing I can recommend is to try to do the separate parts of the assignment one at a time.
Pick a part, figure the program steps needed to do it, write the code, compile and test.
When that works, move on to the next part.
ok thank you for the advice
hi,
Divide and conquer. I read your post and is too much in order to implement or search a solution.
_______________
Oscar Gómez
Engineer at PSL
PSL S.A. - CMMi 5 nearshore software development and IT outsourcing from Latin America - Home