I am trying to update my board (consisting of three arraylists in an arraylist) whenever a player inputs a number. The number corresponds to a square on the board in the following way:
1 2 3
4 5 6
7 8 9
I am having trouble updating the grid.
Function
public static void playBoard(int choice, ArrayList<ArrayList<String>> board, boolean playerTurn) {
String val;
if (!playerTurn) {
val = "| X |";
}
else {
val = "| O |";
}
if (choice>=1 && choice<=3) {
System.out.println("H");
ArrayList<String> updateRow = board.get(0);
if (choice ==3) {
val+="\n";
}
updateRow.set(choice-1, val);
System.out.println(updateRow);
board.set(0, updateRow);
System.out.println(display(board));
}
else if (choice>=4 && choice<=6) {
System.out.println("H");
ArrayList<String> updateRow = board.get(1);
if (choice ==6) {
val+="\n";
}
updateRow.set((choice-4), val);
board.set(1, updateRow);
System.out.println(display(board));
}
else if (choice>=7 && choice<=9) {
System.out.println("H");
ArrayList<String> updateRow = board.get(2);
if (choice ==9) {
val+="\n";
}
updateRow.set(choice-7, val);
board.set(2, updateRow);
System.out.println(display(board));
}
else {
System.out.println("Input out of range");
return;
}
}
The problem is that when the user inputs a value, that entire column in which the value corresponds to is updated instead of the individual square.
I have checked that:
- Only one if statement is triggered.
- The update occurs only once
- The update occurs upon the correct index.
Through my debugging, I believe the problem line is:
updateRow.set(choice-1, val);
When the user (Player 1) inputs 1:
Expected Output
| X || - || - |
| - || - || - |
| - || - || - |
Actual Output
| X || - || - |
| X || - || - |
| X || - || - |
Display function
Sorry, I didn't realize you guys needed to see this other function
public static String display(ArrayList<ArrayList<String>> board) {
StringBuilder builder = new StringBuilder();
for (ArrayList<String> row : board) {
for (String space: row) {
builder.append(space);
}
}
String text = builder.toString();
return text;
}
The problem seems in the creation: you probably used the same column ArrayList object for every row.
// Error:
ArrayList<String> row = new ArrrayList<>();
row.add("...");
row.add("...");
row.add("...");
for (int i = 0; i < 3; ++i) {
board.add(row);
}
should have been:
for (int i = 0; i < 3; ++i) {
ArrayList<String> row = new ArrrayList<>();
row.add("...");
row.add("...");
row.add("...");
board.add(row);
}
The same conceptual error means: it is not needed to do:
board.set(2, updateRow); // Not needed.
Changing the entry in the updateRow object held by the board is done by reference.
Some tips:
- Here one can use
String[][]. - It is easier to separate display/view (the strings) from the data model (a char?),
so maybe
char[][] board = new char[3][3];