为什么此代码不打印应有的内容？

Question

This code should draw table, but it doesn't. Why? The code compiles but it doesn't print enything. Here is code:

 import java.util.Arrays;

    public class Nizovi{

    public static char table[][]= new char[10][10] ;



    public static void drawTable(){
        // this should draw table   

        int k=1;
        while(k <= 30){
            System.out.print("-");
        }
        System.out.println();

        for(int i=0; i < table.length; i++){

            for(int j=0; j < table[i].length; j++){
                System.out.print("|"+ table[i][j] + "|");
            }

            System.out.println();

        }

        k=1;
        while(k <= 30){
            System.out.print("-");
        }

    }


    public static void buildTable(){
        // and this is supposed to fill it with *    
        for(char[] row: table){
            Arrays.fill(row, '*');
        }
    }

    public static void main (String[] args){

        Nizovi.buildTable();
        Nizovi.drawTable();

    }
    }

I can't see what i miss. What's wrong here?

Answer 1

Your loop says while(k <= 30)... - how is k ever to reach 30? Nothing is changing it.

Answer 2

Increment k inside the while blocks:

 while(k <= 30){
        System.out.print("-");
        k++; // add this to your loops
 }

In your code, k is not updated within the loops, it therefore remains 1 and stays always less-or-equal to 30 ( k <= 30 always yields true )

know as "an endless loop"

Output with incrementing the k references within the while -blocks:

------------------------------
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
|*||*||*||*||*||*||*||*||*||*|
------------------------------

(Make sure you update both while -blocks (hence the plural))

Answer 3

The while loop is different from for loop. for assumes you are going to do something a certain amount of times and can therefore automatically increment the index by executing the i++ part. while only checks if the condition is fulfilled. Therefore you should take care of the state of the condition and increment the counter k in the body of the while loop by yourself.

Answer 4

increment k in while loop

while(k <= 30){
    System.out.print("-");
    k++;
}