在 while 循环中打印数组

Question

I am trying to print my array using a method call once while the user inputs y or Y. I do not know how to get the array to only print once.

I've researched and tried tweaking my own code but I am lost.

public class Lab10p1 {
public static final int ROW = 5;
public static final int COL = 6;
public static final int MIN = 0;
public static final int MAX = 100;

/**
* @param args the command line arguments
*/
public static void main(String[] args) 
{
    Scanner scan=new Scanner(System.in);
    System.out.println("Do you want to start Y/N?");
    char c =scan.next().charAt(0);

    while(c=='y'||c=='Y')
    {
        int[][] a = new int[ROW][COL]; 
        randArray(a, ROW, COL, MIN, MAX);
    }
}

public static void randArray(int[][] matrix, int row, int col, int low, int up)
{     
    Random rand = new Random();   
    for (int r = 0; r < row; r++)
    {          
        for (int c = 0; c < col; c++)   
        {         
            int are=matrix[r][c] = rand.nextInt(up - low + 1) + low; 
            System.out.print(" "+are); 
        }       
        System.out.println();
    }
}

the expected output is

Do you want to continue(Y/N): y
The array elements are:
12 31 12 21 45 23
32 12 67 54 35 67
34 54 33 34 53 34
23 34 43 23 45 78
23 54 89 76 54 34

The actual results are an infinite loop of printing 6x5 arrays

Answer 1

You should use if instead of while . If the user enters Y or y , the loop will never finish because c is never set to anything else but Y or y inside the loop and therefore the loop condition is always true.

If you want to ask the user again after each printed array, you have to include the question into the loop, but in this case I would prefer a do while loop.

Answer 2

Once you print the array . prompt user to input character again so if he/she inputs Y again the print array again like:

while(c=='y'||c=='Y')
{
    int[][] a = new int[ROW][COL]; 
    randArray(a, ROW, COL, MIN, MAX);
    System.out.println("Do you want to start Again Y/N?");
    c = scan.next().charAt(0);
}

Or if you want your program to run only once then replace while with if .

Answer 3

That is happening because you input the value of 'c' only once and keep iterating it, now it goes into infinite loop because the value of 'c' doesn't change at all.

char c =scan.next().charAt(0);
int[][] a;
while(c=='y'||c=='Y')
{

a = new int[ROW][COL]; 
randArray(a, ROW, COL, MIN, MAX);
c =scan.next().charAt(0);
}

Also, you don't have to redeclare the 2D array each time.

---

Also, you can use a do-while loop which is more suitable for such cases.

Answer 4

two ways

 if(c=='y'||c=='Y')
{
    int[][] a = new int[ROW][COL]; 
    randArray(a, ROW, COL, MIN, MAX);
}

or

 while(c=='y'||c=='Y')
{
    int[][] a = new int[ROW][COL]; 
    randArray(a, ROW, COL, MIN, MAX);
    break;
}