Question

(IN JAVA) Write a program named Review.java and implement the following methods:

public static boolean isValidTicTacToeBoardString(String str)
This method takes as its parameter a String that contains 9 characters representing the status of the Tic Tact Toe game. The String is mixed with X, O, x, o, and other letters. The first three letters represent the first row, letter 4 through letter 6 represent the second row, and the rest for the last row. To be considered as a valid status, the String must meet the following condistions:

1. The absolute difference between the number of Xs and the number of Os must be either 0 or 1
2. There is only one or none player meeting the "win" condition (row, colum, diagonal)

public static char[][] buildTicTactToe2DBoard(String str)

This method takes as its parameter a String that contains 9 characters. The String is mixed with X, O, x, o, and other letters. If the argument string is valid board string, then construct a 2D arrray to represent the board. Use a peroid (.) to replace all other letters in the 2D array. For example, the string "XX9pOoOxR" should return the following 2D array:
X  X  .
.    O  O
O  X   .


public static int countWord(String word, File file)
This method counts and returns the number of occurrence of the word in the file. A data file: wordCOunt.txt is provided for testing.

public static int[] coutingGrades(File file)
This method takes as its parameter a file containing grades for a class, then counts how many grades are in each of the following categories and returns them as a 5-element int array:

[90 - 100]
[80 - 89]
[70 - 79]
[60 - 69]
[Below 60]

This method returns 
Design a java program named GradeCount.java to read data from a gradebook (gradebook.txt contains grades only) and count how many students are in each of the following categories:
90 - 100
80 - 89
70 - 79
60 - 69
Below 60

Here is the sample data file:

82 100 88 90 56 76 67 60 2000
98 65 90 85 67 81 93 86 88B
87 70 88 78 84 76 81 89 

Please note the file may contains some invalid data and your program should discard those invalid data: less than 0 or greater than 100, or non-numerical data.

Once completed, please run Grader.class to test your program and record the result in result.txt under the assignment folder.

Answer 1

Answered the first question regarding methods for Tic tac toe game as per Chegg's answering guidelines.

Hope this helps! Comment in case of a doubt.

All the explanation is in the code comments.

Code:

public class Main
{
// 1st required function
public static boolean isValidTicTacToeBoardString(String str) {
  
// first check for the length of the string
if(str.length() != 9)
return false;
  
// now count the Xs and Os
int count_x = 0, count_o = 0;
for(int i=0; i<9; i++) {
  
char ch = str.charAt(i);
  
// for X character
if(ch == 'X' || ch == 'x')
count_x++;
  
// for O character
if(ch == 'O' || ch == 'o')
count_o++;
}
  
// check for absolute difference
if(!(Math.abs(count_o - count_x) == 1 || (count_o - count_x) == 0))
return false;
  
// finally checking for winning conditions
boolean win_x = false, win_o = false;
char ch1, ch2, ch3;
  
// check for the horizontal rows
for(int i=0; i<9; i+=3) {
ch1 = str.charAt(i);
ch2 = str.charAt(i+1);
ch3 = str.charAt(i+2);
  
// all characters match
if(ch1 == ch2 && ch2 == ch3) {
  
if(ch1 == 'X' || ch1 == 'x')
win_x = true;
if(ch1 == 'O' || ch1 == 'o')
win_o = true;
}
}
  
// check for the vertical columns
for(int i=0; i<3; i++) {
ch1 = str.charAt(i);
ch2 = str.charAt(i+3);
ch3 = str.charAt(i+6);
  
// all characters match
if(ch1 == ch2 && ch2 == ch3) {
if(ch1 == 'X' || ch1 == 'x')
win_x = true;
if(ch1 == 'O' || ch1 == 'o')
win_o = true;
}
}
  
// for the 2 diagonals
ch1 = str.charAt(0);
ch2 = str.charAt(4);
ch3 = str.charAt(8);
// all characters match
if(ch1 == ch2 && ch2 == ch3) {
if(ch1 == 'X' || ch1 == 'x')
win_x = true;
if(ch1 == 'O' || ch1 == 'o')
win_o = true;
}
  
ch1 = str.charAt(2);
ch2 = str.charAt(4);
ch3 = str.charAt(6);
// all characters match
if(ch1 == ch2 && ch2 == ch3) {
if(ch1 == 'X' || ch1 == 'x')
win_x = true;
if(ch1 == 'O' || ch1 == 'o')
win_o = true;
}
  
// only one or none should be true => if both are true, invalid
if(win_x && win_o)
return false;
  
return true;
}
  
public static char[][] buildTicTactToe2DBoard(String str) {
  
// first check for valid board
if(!isValidTicTacToeBoardString(str))
return null;
  
// construct a 2D arrray to represent the board
char board[][] = new char[3][3];
  
// loop for all characters
for(int i=0; i<9; i++) {
  
char ch = str.charAt(i);
  
// for X character
if(ch == 'X' || ch == 'x')
board[i/3][i%3] = 'X';
  
// for O character
else if(ch == 'O' || ch == 'o')
board[i/3][i%3] = 'O';
  
else // all other characters
board[i/3][i%3] = '.';
}
  
// return the character board
return board;
}
  
   public static void main(String[] args) {
      
       // sample run
       String str = "XX9pOoOxR";
      
       // call the buildTicTactToe2DBoard() method
       char board[][] = buildTicTactToe2DBoard(str);
      
       // if board is null => invalid str board string
       if(board == null) {
       System.out.println("Invalid TicTacToe Board String");
       } else {
       // print the Board
       for(int i=0; i<3; i++) {
       for(int j=0; j<3; j++) {
       System.out.print(board[i][j] + " ");
       }
       System.out.println();
       }
       }
      
   }
}

Sample run:

For str = "XX9pOoOxR"

Code screenshots: