I know my code is a little messy but I will try to be as detailed as possible. The code is creating a TicTacToe game. I am using an array to create the game board which is the gameBoard(). The user is always X while the computer is always O. I've created if statements for the user input and the computer input, the difference is, the computer gets its number from java.util.Random. The if statements grab the user's input and prints an X on the board where designated, same with the computer. The problem here is when the random generator chooses a space where an X is already present, it overlaps and vice versa. I need the program to secretly tell the computer to generate another random number. If you can help it would be great. Sorry for the big description.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.Random;
public class TicTacToeGame {
static String arrayPicture[][]; //Array is universal so we can include it into any method
static int userInput;
static boolean validInput = false;
static String name;
public static void main (String[] args) throws IOException {
System.out.println ("Please enter your name:");
name = gameStart("");
arrayPicture = new String [13][13];
for (int i = 0; i < 13; i ++) {
for (int j = 0; j < 13; j ++) {
arrayPicture [i][j] = " "; //Print spaces into the array
}
}
while (validInput == false) {
validX();
cpuPlacement();
System.out.println ("Computer, please enter your number");
validInput = false;
}
}//main
public static void verticalLine (int x1, int y1, int x2) {
for (int k = x1; k < x2; k ++) {
arrayPicture [y1][k] = "|"; //if y1 and k are present, print a vertical line in the array
}
}//verticalLine
public static void horizontalLine (int x1, int y1, int x2) {
for (int k = x1; k < x2; k ++) {
arrayPicture [y1][k] = "-"; //if y1 and k are present, print a dash in the array
}
}//horizontalLine
public static void printArray () {
for (int i = 0; i < 13; i ++) {
for (int j = 0; j < 13; j ++) {
System.out.print (arrayPicture[i][j]);
}
System.out.println();
}
}//printArray
public static String gameStart (String input) throws IOException {
boolean validInput = false;
BufferedReader userInput = new BufferedReader (new InputStreamReader(System.in));
while (validInput == false) {
input = userInput.readLine();
validInput = true;
System.out.println ("The name of the game is TicTacToe, you will always be the letter X.");
System.out.println ("Please choose the coordinates you wish. The coordinates are where your X will be placed on the game board.");
}
return input;
}
public static void validX () throws IOException {
gameBoard();
String input = null;
System.out.println (name + ", please enter your number");
try {
BufferedReader columnNumber = new BufferedReader (new InputStreamReader(System.in));//BufferedReader variable where the user will input their answer
input = columnNumber.readLine();
userInput = Integer.parseInt (input);
validInput = true;
userPlacement();
//If an exception is present, the try sends it to catch.
//Ex. If the user in\puts "bob has a cat" the try will find an exception and immediately send it to the catch statement
}
catch (NumberFormatException ex) {
System.out.println ("Invalid input, please enter a number.");
validInput = false;
}
if (userInput == 1) {
userInputX (2, 2, 3);
}
else if (userInput == 2) {
userInputX (6, 2, 7);
}
else if (userInput == 3) {
userInputX (10, 2, 11);
}
else if (userInput == 4) {
userInputX (2, 6, 3);
}
else if (userInput == 5) {
userInputX (6, 6, 7);
}
else if (userInput == 6) {
userInputX (10, 6, 11);
}
else if (userInput == 7) {
userInputX (2, 10, 3);
}
else if (userInput == 8) {
userInputX (6, 10, 7);
}
else if (userInput == 9) {
userInputX (10, 10, 11);
}
}
public static void cpuinputO (int x1, int y1, int x2) throws IOException {
gameBoard();
for (int k = x1; k < x2; k ++) {
arrayPicture [y1][k] = "O"; //if y1 and k are present, print a dash in the array
}
}
public static void userInputX (int x1, int y1, int x2) {
for (int k = x1; k < x2; k ++) {
arrayPicture [y1][k] = "X"; //if y1 and k are present, print a dash in the array
}
}
public static void userPlacement () throws IOException {
if (userInput == 1) {
userInputX (2, 2, 3);
}
else if (userInput == 2) {
userInputX (6, 2, 7);
}
else if (userInput == 3) {
userInputX (10, 2, 11);
}
else if (userInput == 4) {
userInputX (2, 6, 3);
}
else if (userInput == 5) {
userInputX (6, 6, 7);
}
else if (userInput == 6) {
userInputX (10, 6, 11);
}
else if (userInput == 7) {
userInputX (2, 10, 3);
}
else if (userInput == 8) {
userInputX (6, 10, 7);
}
else if (userInput == 9) {
userInputX (10, 10, 11);
}
}
public static void cpuPlacement () throws IOException {
Random random = new Random();
int cpuCoordinates = random.nextInt(10);
System.out.println (cpuCoordinates);
boolean validInput0 = false;
if (validInput0 == true) {
if (cpuCoordinates < 1) {
validInput0 = false;
}
}
else if (cpuCoordinates == 1) {
cpuinputO (2, 2, 3);
}
else if (cpuCoordinates == 2) {
cpuinputO (6, 2, 7);
}
else if (cpuCoordinates == 3) {
cpuinputO (10, 2, 11);
}
else if (cpuCoordinates == 4) {
cpuinputO (2, 6, 3);
}
else if (cpuCoordinates == 5) {
cpuinputO (6, 6, 7);
}
else if (cpuCoordinates == 6) {
cpuinputO (10, 6, 11);
}
else if (cpuCoordinates == 7) {
cpuinputO (2, 10, 3);
}
else if (cpuCoordinates == 8) {
cpuinputO (6, 10, 7);
}
else if (cpuCoordinates == 9) {
cpuinputO (10, 10, 11);
}
}
public static void gameBoard () throws IOException {
System.out.println (" ");
horizontalLine (1, 0, 4); horizontalLine (5, 0, 8); horizontalLine (9, 0, 12);
verticalLine (0, 1, 1); verticalLine (4, 1, 5); verticalLine (8, 1, 9); verticalLine (12, 1, 13);
verticalLine (0, 2, 1); verticalLine (4, 2, 5); verticalLine (8, 2, 9); verticalLine (12, 2, 13);
verticalLine (0, 3, 1); verticalLine (4, 3, 5); verticalLine (8, 3, 9); verticalLine (12, 3, 13);
horizontalLine (1, 4, 4); horizontalLine (5, 4, 8); horizontalLine (9, 4, 12);
verticalLine (0, 5, 1); verticalLine (4, 5, 5); verticalLine (8, 5, 9); verticalLine (12, 5, 13);
verticalLine (0, 6, 1); verticalLine (4, 6, 5); verticalLine (8, 6, 9); verticalLine (12, 6, 13);
verticalLine (0, 7, 1); verticalLine (4, 7, 5); verticalLine (8, 7, 9); verticalLine (12, 7, 13);
horizontalLine (1, 8, 4); horizontalLine (5, 8, 8); horizontalLine (9, 8, 12);
verticalLine (0, 9, 1); verticalLine (4, 9, 5); verticalLine (8, 9, 9); verticalLine (12, 9, 13);
verticalLine (0, 10, 1); verticalLine (4, 10, 5); verticalLine (8, 10, 9); verticalLine (12, 10, 13);
verticalLine (0, 11, 1); verticalLine (4, 11, 5); verticalLine (8, 11, 9); verticalLine (12, 11, 13);
horizontalLine (1, 12, 4); horizontalLine (5, 12, 8); horizontalLine (9, 12, 12);
printArray ();
}//gameBoard
}//public class
I'm not quite sure what's going on in your code (why are you cycling through a 13-by-13 array for Tic-Tac-Toe?) but this should be an easy fix. The simplest fix would be to add a while loop around your CPU placement code instead of your current if/else-if statement. (The if/else-ifs should be inside the while loop.) When a valid placement is found,
while(validInput0==false){
if(cpuCoordinates == 1){
if(squareOneOwner == null){
squareOneOwner = "CPU"
validInput0 = true;
}
}else if(...){
...
}
if(validInput0 == false){
cpuCoordinates = random.nextInt(10);
}
}
etc. This lets you check whether the square the computer is aiming for and only claim it if it's currently empty. It requires some changes elsewhere, but they're simple enough. The last if statement will reroll for the next cycle if the previous attempt was invalid.