在Java中将随机字母放入二维数组中

Question

I am suppose to create a 2 dimensional array that contains alphabetical letters that are all capitalized. The goal of the program is basically building a word search puzzle, and I want to fill the 2 dimensional arrays with random alphabetical letters but with the code that I have currently, the table array just fills out completely with one alphabetical letter that is randomly generated. Is there a way to fill the array with random letters randomly?

import java.util.*;
public class puzzle
{
    public static void main
    {
       box();
       //other methods

       public static void box()
       {
          int rows = 10;
          int columns = 10;  
          int number = (int) (Math.random() * 26) + 65;    
          char[][] table = new char [rows][columns];
          for (int r = 0; r < rows; r++)
          {
             for (int c = 0; c < columns; c++)
             {
                table[r][c] = (char) number; 
                System.out.print(table[r][c] + " ");
             } //inner for loop
             System.out.println();
          } //outer for loop
       }
    }
}

This code is able to print

Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q
Q Q Q Q Q Q Q Q Q Q

or

V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V
V V V V V V V V V V

and I want it to be something like

A G E C H J E Q D Z
G H K E Q E N M E J
H I Z E K H E Q K H
B Y U M G A E K H M
N Q A Y R Y E C U E
Y D W H X S J R S W
I Y O B N M K G D E
A D J R E X C B N G
W R U I G D D G J F
X C V O E W Q A O P

Any help would be appreciated.

Answer 1

Bring your number inside loop.

 char[][] table = new char [rows][columns];
 for (int r = 0; r < rows; r++){
    for (int c = 0; c < columns; c++){
       int number = (int) (Math.random() * 26) + 65;  //just move this line
       table[r][c] = (char) number; 
       System.out.print(table[r][c] + " ");
    }//inner for loop
    System.out.println();
 }//outer for loop

Answer 2

Just move this

int number = (int) (Math.random() * 26) + 65; 

to just before

table[r][c] = (char) number;   

then it will get a new value for each loop

Answer 3

You only generate one character (outside your loop) with a temporary value. Also, I would prefer 'A' to a constant 65 . Like,

 for (int r = 0; r < rows; r++){
    for (int c = 0; c < columns; c++){
       table[r][c] = (char) ('A' + (Math.random() * 26));
       System.out.print(table[r][c] + " ");
    }
 }

Answer 4

you are generating a random number only once, here int number = (int) (Math.random() * 26) + 65;

after that, you loop and insert the same number to each location on your 2d-array. If int number = (int) (Math.random() * 26) + 65; was inside the loop, you would get a random number each iteration, and that way, you would have (theoratically) different numbers.

So, just change

  public static void box(){
 int rows = 10;
 int columns = 10;  
 int number = (int) (Math.random() * 26) + 65;   // move this into loop 
 char[][] table = new char [rows][columns];
 for (int r = 0; r < rows; r++){
    for (int c = 0; c < columns; c++){
       table[r][c] = (char) number; 
       System.out.print(table[r][c] + " ");
    }//inner for loop
    System.out.println();
 }//outer for loop

into

  public static void box(){
     int rows = 10;
     int columns = 10;  

     char[][] table = new char [rows][columns];
     for (int r = 0; r < rows; r++){
        for (int c = 0; c < columns; c++){
           int number = (int) (Math.random() * 26) + 65;
           table[r][c] = (char) number; 
           System.out.print(table[r][c] + " ");
        }//inner for loop
        System.out.println();
     }//outer for loop

Also, you can put the two lines togather and remove the need for number local variable:

table[r][c] = (int) (Math.random() * 26) + 65;

Another thing I would have changed is using 'A' instead of 65. It makes it clearer in my opinion... table[r][c] = (int) (Math.random() * 26) + 'A';