Question

I get multiple errors on my code, I'm pretty sure I completed everything as directed. Can someone tell me what I did or didn't do?

Answer 1

/**
* Represents and maintains a Tic-Tac-Toe board. Accepts move input in various
* forms and throws exceptions for invalid or illegal entries. Places
* valid moves and determines if the game has been won. Displays the board
* contents.
*/
public class TicTacToeBoard {
private final char[][] grid = new char[3][3];
public static final char SPACE = ' ';

/**
* Fills the grid with space characters.
*/
public TicTacToeBoard() {
/** Make a call to clearGrid() here. */
clearGrid();
}

/**
* Validates a human player's String input for a move.
* @param input A string that is expected to be a two-character keyboard
* entry from the user representing a row and a column.
* @param mark The mark (X or O) the calling Player wishes to place on the
* board.
* @return <code>true</code> if the move resulted in a winning game,
* <code>false</code> otherwise.
* @throws InvalidInputException if the input is not two characters
* long and does not contain a valid letter for the first character
* and a valid number for the second character, both within the range
* of the board.
* @throws IllegalMoveException if the move attempts to place a mark
* on a space that is already occupied.
*/
public boolean move(String input, char mark) throws InvalidInputException ,
IllegalMoveException {
/**
* Check for the following cases.
* 1. If the input is null, throw a NullInputException.
* 2. The input must have exactly two characters. If it does not,
* throw a default InvalidInputException.
* 3. The first character of the input must be a letter indicating a
* row on the board: 'A' through 'C'. The user can enter this data
* as uppercase or lowercase. The second character of the input must
* be a number indicating a column on the board: '1' through '3'. If
* the characters do not meet these specifications, throw a
* default InvalidInputException.
*/

if(input == null) {
throw new NullInputException();
}

if(input.length() != 2) {
throw new InvalidInputException();
}

input = input.toUpperCase();
if( (input.charAt(0) != 'A' && input.charAt(0) != 'B' && input.charAt(0) != 'C') || // If the first character is invalid
(input.charAt(1) != '1' && input.charAt(1) != '2' && input.charAt(1) != '3') ) {
throw new InvalidInputException();
}

/**
* Find a way to convert the characters in the input to variables of
* type int that correspond to rows and columns in the grid. Assign
* these values to variables row and col. For example, if the input
* is "A3", the row would be 0 and the col would be 2.
*/
int row;
int col;
row = input.charAt(0) - 'A';
col = input.charAt(1) - '1';
// Now that we have converted the input to variables of type int for
// row and col, call the move method that processes these values and
// return the results.
/** Uncomment the line below when the code listed above is complete. */
return move(row, col, mark);

/** Temporary return statement. Remove when code above is complete. */
// return false;
}

/**
* Validates and processes row and column int values for a move.
* @param row Value representing the row.
* @param col Value representing the column.
* @param mark The mark (X or O) the calling Player wishes to place on the
* board.
* @return <code>true</code> if the move resulted in a winning game,
* <code>false</code> otherwise
* @throws IllegalMoveException if the move attempts to place a
* mark on a space that is already occupied.
*/
public boolean move(int row, int col, char mark)
throws IllegalMoveException {
/**
* 1. Check to see if the incoming move tries to place a mark on a
* space that is already occupied with X or O. If it is, throw
* a default IllegalMoveException.
*
* 2. If no exception was thrown, change the grid character at the
* row, col coordinates to the passed in mark.
*
* 3. Call isWin() and isTie(). If either of these methods returns
* true, return true from move().
*/
if(grid[row][col] == 'X' || grid[row][col] == 'O') {
throw new IllegalMoveException();
}

grid[row][col] = mark;
/** Temporary return statement. Remove when code above is complete. */
return isWin(mark) || isTie();
}

/**
* Returns the character at a specified grid location.
* @param row Value representing the row.
* @param col Value representing the column.
* @return Character at grid location specified by row and column.
*/
public char getSpace(int row, int col) {
/** Return the mark stored at the specified location. */


/** Temporary return statement. Remove when code above is complete. */
return grid[row][col];
}

// The isWin() method records if a game has been won here so isTie()
// can check the result without running isWin() again.
private boolean gameHasBeenWon = false;
/**
* Determines if the board has been won with a specified mark.
* @param mark A mark to search for (X or O).
* @return <code>true</code> if the board has been won by the specified
* mark.
*/
boolean isWin(char mark) {
// If the game has already been recorded as won, return true.
if (gameHasBeenWon) return true;
/**
* Using the incoming mark, implement nested loops to loop through the
* columns and diagonals, checking each character in every column and
* diagonal o see if there are three marks in a line. If any
* winning line is found, complete the following directives:
* 1. Set gameHasBeenWon to true.
* 2. Return the value of gameHasBeenWon.
*
* The check for horizontal wins is provided for you.
*/
// Check for horizontal wins.
for (int row = 0; row < 3; row++) {
boolean win = true;
for (int col = 0; col < 3; col++) {
if (grid[row][col] != mark) win = false;
}
if (win) {
gameHasBeenWon = true;
return gameHasBeenWon;
}
}


// Return false if you have not returned true anywhere.
return false;
}

/**
* Determines if the game has resulted in a tie.
* @return <code>true</code> if the game is a tie.
*/
boolean isTie() {
// If game has already been recorded as won, then it cannot be a tie.
if (gameHasBeenWon) return false;

// If there are any spaces on the board, return false, because it is
// not a tie.
for (int row = 0; row < 3; row++) {
for (int col = 0; col < 3; col++) {
if (grid[row][col] == SPACE) return false;
}
}

// If the game was not won, but all the spaces are full, it is a tie.
return true;
}

final String SPACER = " ";
/**
* Displays the board.
*/
public void display() {
final String CROSSBAR = SPACER + "

Answer 2

@SmokeyBrown when you get a chance would you mind looking at this?

Answer 3

Hi there!
In the screenshot you posted, we see the method defined for validating proper moves: "
public boolean move(String input, char mark) throws InvalidInputException ,
IllegalMoveException
"
In the method declaration, I suspect that including the throw exception statements might be redundant, since those are referenced within the method itself. We can try removing the " throws InvalidInputException , IllegalMoveException " part of that line to see if that helps at all.

What kind of error message are you seeing when you try to compile your code? The IDE might have some hints as well, if you mouse over the sections of code underlined in red.

Answer 4

One of the errors I'm getting is, " Unknown type: NullInputException "

Answer 5

That's a good piece of information. It sounds like the code isn't recognizing all of the exceptions in your code as throwable objects. Hm, but I'm not seeing anything obvious off about your syntax... Let me take another look...
Any other errors, in the meantime?

Answer 6

Nope they are all "Unknown type"

Answer 7

I see. What about when you mouse over "InvalidInputException", "NullInputException", and "IllegalMoveException"? Does your editor give you any suggestions about those objects?

In the section you screenshotted, it seems like the move() method does not actually throw any IllegalMoveException, so we should be able to remove that from the method declaration. Inversely, that same method does throw NullInputException, so we may want to include that in the method declaration instead

Answer 8

They say "Unknown Type: InvalidInputException" "Unknown Type: NullInputException"
"Unknown Type: IllegalMoveException"

Answer 9

Now, I notice that you also have exceptions in other parts of the code as well. Are you getting error messages for those sections or is it just this part of your program?

Answer 10

Now, I haven't had to do this before, but the error messages seem indicate that the exceptions you're trying to throw are not a recognized type. Maybe the error would be resolved by type-casting the exceptions so that their type is explicitly known? It's kind of a long-shot, and I'm kind of just curious to see what would happen. Maybe something like
"throw new (throwable)NullInputException() " ?

It does seem like your code for throwing exceptions is written properly, which is why I asked whether you're seeing similar areas in other sections of the program. Maybe comparing the exceptions that do work to the ones that don't can offer some hints? It might be something subtle we're missing in another section altogether