What is each line of code doing in this Java Program? Please explain line by lin

Question

What is each line of code doing in this Java Program? Please explain line by line.

/*
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*/
package tictactoe.java;

import java.util.Scanner;

public class TicTacToeJava {
  
public static Scanner sc = new Scanner(System.in); /**
* @param args the command line arguments
*/
public static void main(String[] args) {
  
final int SIZE = 3;
char[][] board = new char[SIZE][SIZE]; // game board

resetBoard(board); // initialize the board (with ' ' for all cells)

// First, welcome message and display the board.
System.out.println("===== WELCOME TO THE TIC-TAC-TOE GAME!! ===== ");
showBoard(board);

// Then ask the user which symbol (x or o) he/she wants to play.
System.out.print(" Which symbol do you want to play, "x" or "o"? ");
char userSymbol = sc.next().toLowerCase().charAt(0);
char compSymbol = (userSymbol == 'x') ? 'o' : 'x';

// Also ask whether or not the user wants to go first.
System.out.println();
System.out.print(" Do you want to go first (y/n)? ");
char ans = sc.next().toLowerCase().charAt(0);

int turn; // 0 -- the user, 1 -- the computer
int remainCount = SIZE * SIZE; // empty cell count

// THE VERY FIRST MOVE.
if (ans == 'y') {
turn = 0;
userPlay(board, userSymbol); // user puts his/her first tic
}
else {
turn = 1;
compPlay(board, compSymbol); // computer puts its first tic
}
// Show the board, and decrement the count of remaining cells.
showBoard(board);
remainCount--;

// Play the game until either one wins.
boolean done = false;
int winner = -1; // 0 -- the user, 1 -- the computer, -1 -- draw

while (!done && remainCount > 0) {
// If there is a winner at this time, set the winner and the done flag to true.
done = isGameWon(board, turn, userSymbol, compSymbol); // Did the turn won?

if (done)
winner = turn; // the one who made the last move won the game
else {
// No winner yet. Find the next turn and play.
turn = (turn + 1 ) % 2;

if (turn == 0)
userPlay(board, userSymbol);
else
compPlay(board, compSymbol);

// Show the board after one tic, and decrement the rem count.
showBoard(board);
remainCount--;
}
}

// Winner is found. Declare the winner.
if (winner == 0)
System.out.println(" ** YOU WON. CONGRATULATIONS!! **");
else if (winner == 1)
System.out.println(" ** YOU LOST.. Maybe next time :) **");
else
System.out.println(" ** DRAW... **");

}

public static void resetBoard(char[][] brd)
{
for (int i = 0; i < brd.length; i++)
for (int j = 0; j < brd[0].length; j++)
brd[i][j] = ' ';
}

public static void showBoard(char[][] brd)
{
int numRow = brd.length;
int numCol = brd[0].length;

System.out.println();

// First write the column header
System.out.print(" ");
for (int i = 0; i < numCol; i++)
System.out.print(i + " ");
System.out.print(' ');

System.out.println(); // blank line after the header

// The write the table
for (int i = 0; i < numRow; i++) {
System.out.print(i + " ");
for (int j = 0; j < numCol; j++) {
if (j != 0)
System.out.print("|");
System.out.print(" " + brd[i][j] + " ");
}

System.out.println();

if (i != (numRow - 1)) {
// separator line
System.out.print(" ");
for (int j = 0; j < numCol; j++) {
if (j != 0)
System.out.print("+");
System.out.print("---");
}
System.out.println();
}
}
System.out.println();
}

public static void userPlay(char[][] brd, char usym)
{
System.out.print(" Enter the row and column indices: ");
int rowIndex = sc.nextInt();
int colIndex = sc.nextInt();

while (brd[rowIndex][colIndex] != ' ') {
System.out.print(" !! The cell is already taken. Enter the row and column indices: ");
rowIndex = sc.nextInt();
colIndex = sc.nextInt();
}

brd[rowIndex][colIndex] = usym;
}

public static void compPlay(char[][] brd, char csym)
{
// Find the first empty cell and put a tic there.
for (int i = 0; i < brd.length; i++) {
for (int j = 0; j < brd[0].length; j++) {
if (brd[i][j] == ' ') { // empty cell
brd[i][j] = csym;
return;
}
}
}
}

public static boolean isGameWon(char[][] brd, int turn, char usym, char csym)
{
char sym;
if (turn == 0)
sym = usym;
else
sym = csym;

int i, j;
boolean win = false;

// Check win by a row
for (i = 0; i < brd.length && !win; i++) {
for (j = 0; j < brd[0].length; j++) {
if (brd[i][j] != sym)
break;
}
if (j == brd[0].length)
win = true;
}

// Check win by a column
for (j = 0; j < brd[0].length && !win; j++) {
for (i = 0; i < brd.length; i++) {
if (brd[i][j] != sym)
break;
}
if (i == brd.length)
win = true;
}

// Check win by a diagonal (1)
if (!win) {
for (i = 0; i < brd.length; i++) {
if (brd[i][i] != sym)
break;
}
if (i == brd.length)
win = true;
}

// Check win by a diagonal (2)
if (!win) {
for (i = 0; i < brd.length; i++) {
if (brd[i][brd.length - 1 - i] != sym)
break;
}
if (i == brd.length)
win = true;
}

// Finally return win
return win;
}
}
  

Explanation / Answer

//package tictactoe.java;//package
import java.util.Scanner;
public class TicTacToeJava {
  
public static Scanner sc = new Scanner(System.in); //to read input...
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
  
final int SIZE = 3;
char[][] board = new char[SIZE][SIZE]; // game board
resetBoard(board); // initialize the board (with ' ' for all cells)
// First, welcome message and display the board.
System.out.println("===== WELCOME TO THE TIC-TAC-TOE GAME!! ===== ");//printing welcome, game name
showBoard(board);//calling showBoard function...passing array board as parameter
// Then ask the user which symbol (x or o) he/she wants to play.
System.out.print(" Which symbol do you want to play, "x" or "o"? ");//showing symbols to select
char userSymbol = sc.next().toLowerCase().charAt(0);//reading and setting user symbol
char compSymbol = (userSymbol == 'x') ? 'o' : 'x';//setting comp symbol...other one
// Also ask whether or not the user wants to go first.
System.out.println();//printing line
System.out.print(" Do you want to go first (y/n)? ");
char ans = sc.next().toLowerCase().charAt(0);//reading uwer decision
int turn; // 0 -- the user, 1 -- the computer
int remainCount = SIZE * SIZE; // empty cell count//initial empty cel count
// THE VERY FIRST MOVE.
if (ans == 'y') {//if user want to go first then
turn = 0;//setting turn to 0, for user
userPlay(board, userSymbol); // user puts his/her first tic//calling userPlay function
}
else {
turn = 1;//setting comp turn to 1
compPlay(board, compSymbol); // computer puts its first tic//calling comPlay function
}
// Show the board, and decrement the count of remaining cells.
showBoard(board);
remainCount--;//decreasing count
// Play the game until either one wins.
boolean done = false;//variable to denote game over or not
int winner = -1; // 0 -- the user, 1 -- the computer, -1 -- draw
while (!done && remainCount > 0) {//loop runs..until game over or.. remainCount is zero
// If there is a winner at this time, set the winner and the done flag to true.
done = isGameWon(board, turn, userSymbol, compSymbol); // Did the turn won?//checking game over or not
if (done)//if game over
winner = turn; // the one who made the last move won the game//storing winner//
else {//not done
// No winner yet. Find the next turn and play.
turn = (turn + 1 ) % 2;//finding the next turn player|comp
if (turn == 0)//if users turn
userPlay(board, userSymbol);//calling userPlay function
else//if comp turn
compPlay(board, compSymbol);//calling compPlay function
// Show the board after one tic, and decrement the rem count.
showBoard(board);//showing board after each turn
remainCount--;//decreasing count
}
}
// Winner is found. Declare the winner.
if (winner == 0)//if user is winner
System.out.println(" ** YOU WON. CONGRATULATIONS!! **");
else if (winner == 1)//if cpu is winner
System.out.println(" ** YOU LOST.. Maybe next time :) **");
else//if draw
System.out.println(" ** DRAW... **");
}
public static void resetBoard(char[][] brd)//method to reset board..means setting all values in 2d array brd to ' '
{
for (int i = 0; i < brd.length; i++)//traversing all rows
for (int j = 0; j < brd[0].length; j++)//traversing all columns
brd[i][j] = ' ';//setting all values in 2d array brd to ' '
}
public static void showBoard(char[][] brd)//to show the contents of 2d array brd
{
int numRow = brd.length;//getting number rows brd
int numCol = brd[0].length;//getting number of columns in brd
System.out.println();
// First write the column header
System.out.print(" ");
for (int i = 0; i < numCol; i++)
System.out.print(i + " ");//printing column numbers
System.out.print(' ');
System.out.println(); // blank line after the header
// The write the table
for (int i = 0; i < numRow; i++) //traversing all row
{
System.out.print(i + " ");//printing row number and space
for (int j = 0; j < numCol; j++)//traversing all columns///means single row
{
if (j != 0)
System.out.print("|");
System.out.print(" " + brd[i][j] + " ");//printing all elements in ith row
}
System.out.println();
if (i != (numRow - 1)) //after printing last row
{
// separator line
System.out.print(" ");
//printing additional row with---- +
for (int j = 0; j < numCol; j++) {
if (j != 0)
System.out.print("+");
System.out.print("---");
}
System.out.println();
}
}
System.out.println();
}
public static void userPlay(char[][] brd, char usym)//method to set user symbol in board
{
System.out.print(" Enter the row and column indices: ");//asking to enter the position to place ... the symbol
int rowIndex = sc.nextInt();//reading row index
int colIndex = sc.nextInt();//reading col index
while (brd[rowIndex][colIndex] != ' ') //to ask user repeatedly..upto the valid index...which is an empty place..to keep the symbol
{
System.out.print(" !! The cell is already taken. Enter the row and column indices: ");//showing error msg
rowIndex = sc.nextInt();//reading again row index
colIndex = sc.nextInt();//reading again col index
}
brd[rowIndex][colIndex] = usym;//setting user symbol in desired position
}
public static void compPlay(char[][] brd, char csym)//method to set computer symbol in board
{
// Find the first empty cell and put a tic there.
for (int i = 0; i < brd.length; i++) {
for (int j = 0; j < brd[0].length; j++) {
if (brd[i][j] == ' ') { // empty cell//finding first empty cell
brd[i][j] = csym;//placing in empty symbol
return;
}
}
}
}
public static boolean isGameWon(char[][] brd, int turn, char usym, char csym)//method to check game status//checking who won the game
{
char sym;
//checking the last turn
if (turn == 0)//if users
sym = usym;//setting sym to users
else//if comps
sym = csym;//setting sym to comp
int i, j;
boolean win = false;//initially setting win to false
// Check win by a row
for (i = 0; i < brd.length && !win; i++) //traversing rows..//runs upto win is false
{
for (j = 0; j < brd[0].length; j++) //traversing cols.
{//means reading row by row
if (brd[i][j] != sym)//if the i,j th symbol of board is not equals to sym
break;//then breaking loop
}
if (j == brd[0].length)//j is equals to complete row length(ie number of cols)..means one complete row has same symbol
win = true;//then setting win to true
}
// Check win by a column
for (j = 0; j < brd[0].length && !win; j++)//traversing cols.//runs upto win is false
{
for (i = 0; i < brd.length; i++) //traversing rows..
{
//means reading col by col
if (brd[i][j] != sym)//if the i,j th symbol of board is not equals to sym
break;//then breaking loop
}
if (i == brd.length)//i is equals to complete col length(ie number of rows)..means one complete col has same symbol
win = true;//setting win to true
}
// Check win by a diagonal (1)
if (!win) {
for (i = 0; i < brd.length; i++) //traversing diagonally
{
if (brd[i][i] != sym)//if the i,i th symbol of board is not equals to sym
break;//then breaking loop
}
if (i == brd.length)//i is equals to complete length(ie number of rows|cols)..means one diagonal1 has same symbol
win = true;//setting win to true
}
// Check win by a diagonal (2)
if (!win) {
for (i = 0; i < brd.length; i++)//traversing diagonally
{
if (brd[i][brd.length - 1 - i] != sym)//if the i,lenght-1-i th symbol of board is not equals to sym
break;//then breaking loop
}
if (i == brd.length)//i is equals to completelength(ie number of rows|cols)..means one diagonal2 has same symbol
win = true;
}
// Finally return win
return win;
}
}

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