MazeDataFileHandler object reads and writes
* information about a Maze to and from a data file, including
* the maze's dimensions, the starting and finish locations,
* and the locations of the walls.
*
* * The first line of the input file should contain the dimensions of * the maze. Subsequent lines should specify the locations of the * starting location, the finishing location, and the locations of * the walls. The file format is: *
* rows columns * row-pos col-pos (starting location) * row-pos col-pos (finishing location) * row-pos col-pos (walls ... ) * ... * row-pos col-pos ** where
rows and columns are integers
* indicating the number of rows and columns in the maze,
* the first row-pos and col-pos are integers
* indicating the row and column position of the starting location,
* the second row-pos and col-pos are integers
* indicating the row and column position of the finishing location,
* and the rest of the row-pos and col-pos lines
* indicate the row and column positions of walls in the maze.
*
* @author Alyce Brady (based on MBSDataFileHandler)
* @version 29 February 2004
**/
public class MazeDataFileHandler implements GridDataFileHandler
{
// Encapsulated data used to read/write maze info from a file
private LineNumberReader inputReader; // buffered input w/ line number
private StringTokenizer tokenizer; // parses tokens from a line
/** Reads information about a maze from an initial configuration
* data file.
* @param file java.io.File object from which to read
* @throws java.io.FileNotFoundException if file cannot be opened
* @throws RuntimeException if invalid information is read from file
**/
public Grid readGrid(File file)
throws java.io.FileNotFoundException
{
// Open the file for reading.
inputReader = new LineNumberReader(new FileReader(file));
// Read maze dimensions and construct maze.
Maze maze = buildMaze();
// Read starting and ending locations.
Location startLoc = readLocation(maze);
if ( startLoc == null )
throw new RuntimeException("Maze has no starting location (line "
+ inputReader.getLineNumber() + ")");
else
maze.setStartLoc(startLoc);
Location endLoc = readLocation(maze);
if ( endLoc == null )
throw new RuntimeException("Maze has no finishing location (line "
+ inputReader.getLineNumber() + ")");
else
maze.setFinishLoc(endLoc);
// Read wall locations.
readWalls(maze);
return maze;
}
/** Reads maze specifications and constructs maze.
* @throws RuntimeException if invalid maze information is read
**/
private Maze buildMaze()
{
int mazeRows, mazeCols;
try
{
// Read the maze dimensions.
mazeRows = readInt();
mazeCols = readInt();
}
catch (Exception e)
{
throw new RuntimeException("Error reading maze dimensions "
+ "(line "
+ inputReader.getLineNumber() + ")");
}
// Validate maze dimensions.
if ( mazeRows <= 0 || mazeCols <= 0 )
throw new RuntimeException("Maze dimensions must be positive (line "
+ inputReader.getLineNumber() + ")");
// Construct the appropriate bounded maze.
Maze newMaze = new Maze(mazeRows, mazeCols);
return newMaze;
}
/** Reads in a Location object (must be a valid location in
* maze).
* @param maze maze in which location must be valid
* @return the newly created Location object
* @throws RuntimeException if invalid location information is read
**/
private Location readLocation(Maze maze)
{
int row, col;
try
{
// Read the location.
row = readInt();
col = readInt();
}
catch (java.io.EOFException e)
{
// Reached end of file
return null;
}
catch (Exception e)
{
// Convert reading exceptions to MBSException.
throw new RuntimeException("Error reading location (line "
+ inputReader.getLineNumber() + ")");
}
Location loc = new Location(row, col);
// Verify that location is valid in this maze.
if ( maze.isValid(loc) )
return loc;
else
throw new RuntimeException("Location " + loc +
" is not valid in this maze (line "
+ inputReader.getLineNumber() + ")");
}
/** Returns the next token in the file as an integer.
* @return an int containing the next number in the file
* @throws java.io.EOFException if EOF
* @throws java.lang.NumberFormatException if next token is not an int
* @throws java.io.IOException if another type of input error occurs
**/
private int readInt()
throws java.io.IOException
{
// Read in number as string, then convert to integer.
String token = readString();
if ( token == null )
throw new java.io.EOFException();
return Integer.parseInt(token);
}
/** Returns the next token in the file as a string.
* @return a String containing the next token in the file; or null
* if end of file is encountered
* @throws java.io.IOException if an input error occurs
**/
private String readString()
throws java.io.IOException
{
// Read in a new line if there are no more tokens in current line.
while ( tokenizer == null || ! tokenizer.hasMoreTokens() )
{
String line = inputReader.readLine();
// Did we encounter end of file?
if ( line == null )
return null;
tokenizer = new StringTokenizer(line);
}
// Return next token.
return tokenizer.nextToken();
}
/** Reads location information for the walls in the maze and
* constructs the walls.
* @param maze the maze in which walls should be created
* @throws RuntimeException if invalid location information is read
**/
private void readWalls(Maze maze)
{
// Read wall locations until there aren't any more, and construct
// the walls as color blocks. The color blocks add themselves to
// the maze as they are constructed.
Location loc;
while ( (loc = readLocation(maze)) != null )
{
new ColorBlock(Color.black, maze, loc);
}
}
/** Reads information about a maze from an initial configuration
* data file.
* @param maze the maze to save
* @param file java.io.File object from which to read
* @throws UnsupportedOperationException
**/
public void writeGrid(Grid maze, File file)
throws java.io.FileNotFoundException
{
throw new UnsupportedOperationException();
}
}