如何使用 ArrayList 从 Java 中的另一个类调用方法？

Question

I am a total beginner at Java and we have a program to do on Bingo. You have to let the user enter the number of players and each player receives a board. Then a random token is called from another class and you have to use that token to mark it on the board. I don't know how to figure out who won...and there's an error on Mark(). Could anyone help? Thanks.

import java.util.Scanner;
import java.util.ArrayList;
public class Bingo 
{
    public static void main(String[] args) 
    {
     Scanner a = new Scanner(System.in);
     System.out.println("Enter number of players: ");
     int num = a.nextInt();
     ArrayList<Board> player = new ArrayList<Board>();
     for(int i = 0; i < num; i++)
       player.add(new Board());
     Token one = new Token();
     int tempNumber = 0, tempLetter = 0;
     boolean win = false;
     while(win = false)
     {
       tempLetter = one.getLetter();
       tempNumber = one.getNumber();

       char letter;
       if(tempLetter == 0)
       letter = 'B';
       else if(tempLetter == 1)
         letter = 'I';
       else if(tempLetter == 2)
         letter = 'N';
       else if(tempLetter == 3)
         letter = 'G';
       else
         letter = 'O';

       System.out.println("Token: " + tempNumber + letter);
       System.out.println();

       win = player.Mark(tempNumber,tempLetter);
     }
  }
}

Here is the Board class:

public class Board
{
    private int[][] card;
    private int row, column;
    boolean bingo;
    public Board()
    {
        card = new int[5][5];
        for(int i = 0; i < card.length; i++)
            for(int j = 0; j < card[i].length; j++)
                card[i][j] = (int) (Math.random() * 75 + 1);
        card[2][2] = 0;

        for(int i = 0; i < card.length; i++)
            for(int j = 0; j < card[i].length; j++)
            {
                System.out.print(card[i][j] + " ");
                if(j == 4)
                    System.out.println();
            }
    bingo = false; //False
    row = 0;
    column = 0;

}

public boolean Mark(int x, int y)
{   
    for(int i = 0; i < card.length; i++)
        for(int j = 0; j < card[i].length; j++)
        {
            if(card[i][j] == x)
                if(j == y)
                {
                    card[i][j] = 0;
                    row = i;
                    column = j;
                }

        }
    System.out.println("Mark: ");

    for(int i = 0; i < card.length; i++)
        for(int j = 0; j < card[i].length; j++)
        {
            System.out.print(card[i][j] + " ");
            if(j == 4)
                System.out.println();
        }
    Check();
    return bingo;
}

private void Check()
{
    int flagRow = 0, flagColumn = 0, flagDiagonal = 0;
    int tempRow = 0, tempColumn = 0, tempRow1 = 4, tempColumn1 = 4;
    //Diagonal check
    if(row == column)
    {
        while(bingo == false)
        {
            if(card[tempRow][tempColumn] == 0)
            {
                tempRow++;
                tempColumn++;
                flagDiagonal++;
            }
            else if(card[tempRow1][tempColumn1] == 0)
            {
                tempRow1--;
                tempColumn1--;
                flagDiagonal++;
            }

            if(flagDiagonal == 5)
                bingo = true;
            else
            {
                tempRow = 0;
                tempColumn = 0;
                tempRow1 = 4;
                tempColumn1 = 4;
                flagDiagonal = 0;
            }
        }
    }
    //Row and column check
    for(int i = 0; i < card.length; i++)
        for(int j = 0; j < card[i].length; j++)
        {
            if(card[i][column] == 0) //Column check
                flagColumn++;
            if(card[row][j] == 0) //Row check
                flagRow++;
        }

    if(flagRow == 5)
        bingo = true;
    else if(flagColumn == 5)
        bingo = true;
    else
    {
        flagRow = 0;
        flagColumn = 0;
    }

    System.out.println("\nCheck: ");
    for(int i = 0; i < card.length; i++)
        for(int j = 0; j < card[i].length; j++)
        {
            System.out.print(card[i][j] + " ");
            if(j == 4)
                System.out.println();
        }
    System.out.println("Bingo status: " + bingo);
   }
}

And here is the Token class:

import java.util.ArrayList;
import java.util.Random;
public class Token
{
    ArrayList<Integer> number;
    public Token()
    {
        number = new ArrayList<Integer>();
        for(int i = 0; i < 75; i++)
            number.add((int)(Math.random() * 75 + 1));
    }
    public int getNumber()
    {
        Random rand = new Random();
        int temp = number.get(rand.nextInt(number.size()));

        number.remove(temp);
        return temp;
    }

    public int getLetter()
    {
        Random rand = new Random();
        int temp = number.get(rand.nextInt(number.size()));
        if(temp >= 1 && temp <= 15)
            return 0; //B
        else if(temp >= 16 && temp <= 30)
            return 1; //I
        else if(temp >= 31 && temp <= 45)
            return 2; //N
        else if(temp >=46 && temp <= 60)
            return 3; //G
        return 4; //O
    }
}

Thank you everyone! I know...this is a long program.

Answer 1

You're calling player.Mark(tempNumber,tempLetter); where player is an ArrayList<Board> which doesn't have that method. It is defined in the class Board itself.

So you want to get the current Board instance from this list and call Mark on that .

ie win = player.get(currentPlayerIndex).Mark(tempNumber,tempLetter);

Depending on your logic you need some currentPlayerIndex that gets the current Player/Board.

Note: as @opensam mentioned, you need to replace while(win = false) with while(win == false) or else you'll assign false to win and the loop breaks before you can do one iteration.

Answer 2

TL;DR

and there's an error on Mark().

'player' is an instance of ArrayList class whereas Mark(int,int) is a method defined for your class Board. If you want to call method Mark(int,int), you will have to call it via an instance of class Board. If you dont understand what that means then please go through this or this .