How to randomly insert String numbers into an array-Java

Question

I have this array here that takes strings values this is my Puzzle Board View, Right now everything works but the array is hard coded and i need the strings to be generated randomly from 0-4. I have tried to get a random char and put it is as a string but this didn't work. Any tips would be nice.

Random rand = new Random();
char c = (char)(rand.nextInt(5) + '0');
StringBuilder sb = new StringBuilder();
sb.append(c);

String[] debug_board_state  = new String[7];
debug_board_state[0] = "0,3,0,0,3,0,2";
debug_board_state[1] = "1,0,2,0,0,1,2";
debug_board_state[2] = "0,2,0,0,0,0,0";
debug_board_state[3] = "0,0,3,0,3,0,4";
debug_board_state[4] = "2,0,0,0,0,1,0";
debug_board_state[5] = "0,1,0,0,1,0,2";
debug_board_state[6] = "2,0,3,0,0,2,0";

UPDATE.

Thanks to user Answer i was able to get the random matrix, although i ran into another problem, I need do more stuff to the matrix so i don't want to print it out. here is the code

static private final int WIDTH_EASY = 7;
 protected void InitializeEasy() {
      Random rand = new Random();

      String[][] debug_board_state  = new String[7][7];
      for (int row = 0; row < debug_board_state.length; row++) {
          for (int column = 0; column < debug_board_state[row].length; column++) {
              debug_board_state[row][column] = String.valueOf(rand.nextInt(5));
          }
      }

      for (int row = 0; row < debug_board_state.length; row++) {
          for (int column = 0; column < debug_board_state[row].length; column++) {
              System.out.print(debug_board_state[row][column] + " ");
          }
      };

    for (int i = 0; i < WIDTH_EASY; ++i) {
      StringTokenizer tokenizer = new StringTokenizer (debug_board_state[i][i], ",");
      int column = 0;
      while(tokenizer.hasMoreTokens()) {
    String token = tokenizer.nextToken();
    getCurrentState().board_elements[i][column] = new BoardElement();
    getCurrentState().board_elements[i][column].max_connecting_bridges = Integer.parseInt(token);
    getCurrentState().board_elements[i][column].row = i;
    getCurrentState().board_elements[i][column].col = column;

    if (getCurrentState().board_elements[i][column].max_connecting_bridges > 0) {
      getCurrentState().board_elements[i][column].is_island = true;
    }
    ++column;
      }
    }
  }

The string Tokenizer works with 1d array but not with 2d, i need something that will do the same thing as StringTokenizer and apply it to the matrix. I am getting the following error

java.lang.NullPointerException: Attempt to read from field Island_and_Bridges.Hashi.BoardElement[][] Island_and_Bridges.Hashi.BoardState$State.board_elements on a null object reference

Why don't you simply use String[][] for your board, since you insist on it being a String? Also, what didn't work? Figured out why it didn't work? — Shark
– Shark, Commented Apr 10, 2018 at 13:05
2 dimensional array is much better in this situation. You can access it by using array[0][0] = "0" — M_I
– M_I, Commented Apr 10, 2018 at 13:07
I have never worked with 2d arrays could you provide an answer of how i could achieve this? — user8580441
– user8580441, Commented Apr 10, 2018 at 13:09

xingbin · Accepted Answer · 2018-04-10 14:51:07Z

1

Although I think int[][] is a better idea, here is the String[][] solution. You can use String.valueOf(rand.nextInt(5)) to generate element in the matrix:

import java.util.Random;

public class Main {

    public static void main(String[] args) {
        Random rand = new Random();

        String[][] matrix  = new String[7][7];
        for (int row = 0; row < matrix.length; row++) {
            for (int column = 0; column < matrix[row].length; column++) {
                matrix[row][column] = String.valueOf(rand.nextInt(5));
            }
        }

        for (int row = 0; row < matrix.length; row++) {
            for (int column = 0; column < matrix[row].length; column++) {
                System.out.print(matrix[row][column] + " ");
            }
            System.out.println();
        }
    }
}

Update:

for (int row = 0; row < WIDTH_EASY; ++row) {
    for (int column = 0; column < WIDTH_EASY; ++column) {
        getCurrentState().board_elements[row][column] = new BoardElement();
        getCurrentState().board_elements[row][column].max_connecting_bridges = Integer.parseInt(debug_board_state[row][column]);
        getCurrentState().board_elements[row][column].row = row;
        getCurrentState().board_elements[row][column].col = column;
        if (getCurrentState().board_elements[row][column].max_connecting_bridges > 0) {
            getCurrentState().board_elements[row][column].is_island = true;
        }
    }
}

edited Apr 10, 2018 at 14:51

answered Apr 10, 2018 at 13:16

xingbin

28.4k12 gold badges62 silver badges111 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

user8580441 Over a year ago

This is what I'm looking for I never worked with 2d arrays Thanks m8!

user8580441 Over a year ago

How can StringTokenize a 2d array, i have tried this but it doesnt work

for (int i = 0; i < WIDTH_EASY; ++i) {       StringTokenizer tokenizer = new StringTokenizer (debug_board_state[i][i], ",");

user8580441 Over a year ago

To form a matrix, if i try to print them without println(); they are printing in line i need matrix to be in column row format rather than in line if you get me

user8580441 Over a year ago

So what could i use to achive this?

user8580441 Over a year ago

I need to other stuff to the matrix that's why i thought i needed to StringTokenize the matrix in order to have it in a column row format without printing it out tbh i dont raeally need to print the matrix out i need it to be stored in a array vairable

|

Sebastian Karlsson · Accepted Answer · 2018-04-10 13:14:23Z

0

Something like this?

Pseudo-code:

String[][] debug_board_state  = new String[7][7];

for (int x = 0; x < debug_board_state.size(); x++) {
     for (int y = 0; y < debug_board_state[x].size(); y++) {
         debug_board_state[x][y] = new_random_character();
     }
}

answered Apr 10, 2018 at 13:14

Sebastian Karlsson

7451 gold badge9 silver badges19 bronze badges

Comments

A. AMAIDI · Accepted Answer · 2018-04-10 13:19:06Z

0

0-4 lies from 49 to 52 on the ASCII scale:

Random rand = new Random();
char c = (char)(rand.nextInt(4)+49);
StringBuilder sb = new StringBuilder();
sb.append(c+'0');

edited Apr 10, 2018 at 13:19

A. AMAIDI

6,8696 gold badges37 silver badges53 bronze badges

answered Apr 10, 2018 at 13:15

Ninja

2052 silver badges12 bronze badges

1 Comment

user8580441 Over a year ago

And how could i put it into the array i have above?

M_I · Accepted Answer · 2018-04-10 13:32:42Z

0

Maybe, you want something like this:

public void initBoard() {
    Random random = new Random();
    String[][] board = new String[7][7];
    for (int i=0; i < board.size(); i++) {
        for (int j=0; j < board[].size(); j++) {
            board[i][j] = String.valueOf(random.nextInt() % 5);
        }
    }
}

It will initialize your board with random number of String.

edited Apr 10, 2018 at 13:32

answered Apr 10, 2018 at 13:16

M_I

1325 bronze badges

Collectives™ on Stack Overflow

How to randomly insert String numbers into an array-Java

4 Answers 4

8 Comments

Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

8 Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related