help - Simple Matrix-like Code

[whoareyou]

Basically, I have to write a program by using arrays to create a "Matrix"-like animation. The hints that my teacher gave us were that the falling characters, their x coordinates, and their y-coordinates should be stored in arrays. His example program is attached. I just don't know where to start. I know for sure that I will need an array for the characters that I will use. Any help is appreciated .

ps. if I have a string array, will I have to go through each character like this? : {"a", "b", "c", "d", "e" ...}

[Zren]

Make a new object with a string and two numbers for the x,y coordinates. Then use an ArrayList as you'll be adding and removing from it often (or simply reseting a fixed number of characters). The hints that you should be using an object class are when you need to have two or more arrays for a similar thing.

If you haven't learnt objects then stick with what your teach mentioned.

For the letters...
Check out the Random. And googling "random letter java" gives some need tricks: http://www.free2code.net/forums/view/topic7554.html

char ch = (char)(random.nextInt('Z'-'A'+1)+'A')

Alternatively you could have a chracter map and using a random index from it like you were going after.

String chars = "abcdABCD";
chars.substring(1,2) // = b

String[] chars = "absdfas".split("|"); // Split all characters.
chars[1]

Googling "java draw string" or the graphics class should aid you. And for gods sake learn double buffering. Your teachers program made me want to hurl with all that flickering.

[whoareyou]

So, I kind of used a for loop after it generates a random letter and random x-coordinate to begin with ... the y-coordinate changes with the for-loop. But, by doing this, only one character shows up on the screen, and then once it reaches the bottom, the program ends. I can solve that by looping the program infinitely (probably with a while-loop) but how do I display more than one character on the screen at once ? Oh, and I guess I could random the y-coordinate to, so it doesn't all start from the top each time.

[Zren]

Try setting the initial y value as a negative (minimally top-fontHeight) so it appears that the character floats down.

Use a for loop to cycle through each letter per frame.

List<String> letters = new ArrayList<String>();
letters.append("M"); // Add string to list

while (true) {
// Start of frame
// Clear screen
for (String letter : letters) {
// draw letter
}
//End of frame
}

[whoareyou]

lol, i have no idea what you're talking about.

here's my code : no arrays, no nothing yet, just something to start with.

Java:

import java.awt.*; import hsa.Console; public class MatrixCode {     static Console c;     public static void main (String[] args)     {         c = new Console ();         while (true)         {             c.setColor (Color.black);             c.fillRect (0, 0, c.maxx (), c.maxy ());             c.setColor (Color.green);             c.setFont (new Font ("monospaced", Font.BOLD, 20));             int x, y;             x = (int) (Math.random () * c.maxx ());             y = 0;             for (int i = 0 ; i < c.maxy () ; i++)             {                 y = i;                 c.drawString ("M", x, y);             }         }     } }

how am I supposed to implement arrays, and show many characters on the screen at once and make them animate??

[Zren]

Right now you're only dealing with one counter (the variable i). You need to get around having more than one counter going at once. Here's a little exercise to help.

Using a loop of your choice, add 1 to each of the variables, then print the value of the variables to the screen.
int a = 4, b = 6, c = 10;

Now try it using an array.
int arr = new int[] { 4, 6, 10};

[whoareyou]

I did your exercise for practice ... perhaps you could tell me how this relates to the matrix?

Java:

int first = 4;         int second = 6;         int third = 10;         c.println ("Values: " + (first) + ", " + (second) + ", " + (third));         int added = 0;         while (added == 0)         {             first += 1;             second += 1;             third += 1;             added += 1;         }         c.println ("New Values: " + (first) + ", " + (second) + ", " + (third));         int[] arr = {4, 6, 10};         c.print ("Array Values: ");         for (int i = 0 ; i < arr.length ; i++)         {             if (i == arr.length - 1)             {                 c.println (arr [i]);             }             else             {                 c.print (arr [i] + ", ");             }         }         for (int i = 0 ; i < arr.length ; i++)         {             arr [i]++;         }         c.println ("New Array Values: " + (first) + ", " + (second) + ", " + (third));

[whoareyou]

So I came up with something, but it isn't working properly. I mean, it has characters and it goes down the screen but it seems as if the text is right-justified.



This is my code:

Java:

//Create a font object and set the font and color of the characters         //in the falling Matrix code         c.setColor (Color.green);         c.setFont (new Font ("monospaced", Font.BOLD, 20));         //Create an array for the x-coordinates of the characters across the         //top of the screen         int[] xchars = new int [100];         //Create an array for the y-coordinates of the characters going         //down the console screen         int[] ychars = new int [100];         //Create an array to store a list of numbers representing characters in         //the string that stores all of chracters that will be displayed         int[] nchars = new int [100];         //Create a list of characters used in Matrix by storing them in a string         //Individual characters can be accessed by using the subString () method         String str1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890!@#$%^&*()-+][{}\\|'\";:/?.>,<";         //Assign different x, y, and character values to the arrays created with the         //specified length         for (int i = 0 ; i < 100 ; i++)         {             nchars [i] = (int) (Math.random () * str1.length ());             xchars [i] = (int) (Math.random () * c.maxx ());             ychars [i] = (int) (Math.random () * c.maxy ());         }         //Use an infinite while loop to display the characters on the screen         //and change the required character's location         while (true)         {             c.setColor (Color.black);             c.fillRect (0, 0, c.maxx (), c.maxy ());             for (int i = 0 ; i < 100 ; i++)             {                 ychars [i] += 20;                 if (ychars [i] >= c.maxy ())                 {                     nchars [i] = (int) (Math.random () * str1.length ());                     xchars [i] = (int) (Math.random () * c.maxx ());                     ychars [i] = 0;                 }                                 c.setColor(Color.green);                 String str2 = str1.substring (nchars [i]);                 for (int j = 0 ; j < 1 ; j++)                 {                     c.drawString (str2, xchars [i], ychars [i]);                 }             }             Thread.sleep (50);         }

[Zren]

Here:
String str2 = str1.substring (nchars [i]);
Your're using:
http://download.oracle.com/javase/6/docs/api/java/lang/String.html#substring(int)

instead of:
http://download.oracle.com/javase/6/docs/api/java/lang/String.html#substring(int, int)

As for the practice thing, your answers weren't what I was intending, but you understood the logic in your matrix code.

[whoareyou]

Ah yes, thank you very much!