Filereader - Reading >1 char at a time

[richard gallagher]

Hi all,

- This question relates to using a text file to create a game map.
- My current code reads 1 character at a time.

  private TileMap loadMap(String filename)
        throws IOException
    {
        ArrayList lines = new ArrayList();
        int width = 0;
        int height = 0;
 
        // read every line in the text file into the list
        BufferedReader reader = new BufferedReader(
            new FileReader(filename));
        while (true) {
            String line = reader.readLine();
            // no more lines to read
            if (line == null) {
                reader.close();
                break;
            }
 
            // add every line except for comments
            if (!line.startsWith("#")) {
                lines.add(line);
                //added
                System.out.println(line);
                width = Math.max(width, line.length());
            }
        }
 
        // parse the lines to create a TileEngine
        height = lines.size();
        TileMap newMap = new TileMap(width, height);
        for (int y=0; y<height; y++) {
            String line = (String)lines.get(y);
            for (int x=0; x<line.length(); x++) {
                char ch = line.charAt(x);
 
                // check if the char represents tile A, B, C etc.
                int tile = ch - 'A';
                if (tile >= 0 && tile < tiles.size()) {
                    newMap.setTile(x, y, (Image)tiles.get(tile));
                }
 
                // check if the char represents a sprite
                else if (ch == 'o') {
                    addSprite(newMap, coinSprite, x, y);
                }
.......
        

- Is it possible for the filereader to read 2 characters at once?
- Example -

 ....
 // check if the char represents a sprite
                else if (XYZ == 'ao') {
                    addSprite(newMap, coinSprite, x, y);
                    addSprite(newMap, grassSprite, x, y);
                }
   

This way, each "x,y" coordinate (tile) can have more than 1 image at loadup. (using only alpahbet and numerics etc is too limiting)

thankyou

rg
[ March 16, 2008: Message edited by: richard gallagher ]

[Campbell Ritchie]

Originally posted by richard gallagher:

 ....
 // check if the char represents a sprite
                else if (XYZ == 'ao') {
                    addSprite(newMap, coinSprite, x, y);
                    addSprite(newMap, grassSprite, x, y);
                }
   

thankyou

rg

Don't use == to test Strings for equality; use the String class equals() method.
Use "" round Strings, not ''. That code snippet won't compile because of the ''. You can't get two keystrokes into a char like that.

You can read a whole line with a Buffered Reader, or you can use the Scanner class to read a line. A Scanner will read the next char, int, etc., instead if you ask nicely (nextInt() etc), so lots of people use Scanner for simple text files instead of Readers.

You can split the line into a char[] array with a method of the String class (look through the API; it has an obvious name). You could use the charAt() method of String to find different chars within a String instead.

Don't use a break like that. Declare a String line, then

while ((line = reader.readLine()) != null)
{
}//end while

will take care of the reading. You need the extra pair of () to force the = operator to be executed before the != because = has a very low precedence.

Your closing the reader leaves you open to resource leaks if there is an exception. You should use something like this which ensures the reader closes even if there is an IOException

BufferedReader reader = null;
String line;
try
{
   try
   {
       reader = new BufferedReader(new FileReader(fileName);
       while ((line = reader.readLine()) != null
       {
          . . .
       }//end while
   }//end inner try
   finally
   {
      if (reader != null)
      {
         reader.close();
      }//end if. You can close the FileReader too if you wish.
   }//end finally
}//end try
catch ( . . .

The "finally" will make sure to execute that block of code; the != null bit makes sure you only close the reader if it was opened in the first place, and the outer try . . . catch will handle the exceptions.

If you use a Scanner, it consumes Exceptions, but you can get the Exception with its IOException() method.

[Campbell Ritchie]

On reading my last post I notice an error; there is a ) missing from the line starting "while ((line = reader.nextLine()." Sorry.
Also the comment about closing the FileReader only applies of you say

FileReader fileIn = null;
. . .
try
{
   fileIn = new FileReader(fileName);
   reader = new BufferedReader(fileIn);
// etc