How to print a two dimensional array?

Question

I have a [20][20] two dimensional array that I've manipulated. In a few words I am doing a turtle project with user inputting instructions like pen up = 0 and pen down = 1. When the pen is down the individual array location, for instance [3][4] is marked with a "1".

The last step of my program is to print out the 20/20 array. I can't figure out how to print it and I need to replace the "1" with an "X". The print command is actually a method inside a class that a parent program will call. I know I have to use a loop.

public void printGrid() {
    System.out.println...
}

Vidhya - Vidhyadharan · Accepted Answer · 2013-01-09 08:46:44Z

55

you can use the Utility mettod. Arrays.deeptoString();

 public static void main(String[] args) {
    int twoD[][] = new int[4][]; 
    twoD[0] = new int[1]; 
    twoD[1] = new int[2]; 
    twoD[2] = new int[3]; 
    twoD[3] = new int[4]; 

    System.out.println(Arrays.deepToString(twoD));

}

answered Jan 9, 2013 at 8:46

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Vidhya - Vidhyadharan

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1 Comment

Emile Bergeron Over a year ago

Arrays.deepToString do print 2D array but on one line only, as useful as it might be, it's not what the question is about (grid).

Bernhard Barker · Accepted Answer · 2013-11-04 11:41:31Z

27

public void printGrid()
{
   for(int i = 0; i < 20; i++)
   {
      for(int j = 0; j < 20; j++)
      {
         System.out.printf("%5d ", a[i][j]);
      }
      System.out.println();
   }
}

And to replace

public void replaceGrid()
{
   for (int i = 0; i < 20; i++)
   {
      for (int j = 0; j < 20; j++)
      {
         if (a[i][j] == 1)
            a[i][j] = x;
      }
   }
}

And you can do this all in one go:

public void printAndReplaceGrid()
{
   for(int i = 0; i < 20; i++)
   {
      for(int j = 0; j < 20; j++)
      {
         if (a[i][j] == 1)
            a[i][j] = x;
         System.out.printf("%5d ", a[i][j]);
      }
      System.out.println();
   }
}

edited Nov 4, 2013 at 11:41

Bernhard Barker

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answered Oct 16, 2011 at 3:08

COD3BOY

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2 Comments

user997462 Over a year ago

can I replace inside the printGrid method?

COD3BOY Over a year ago

sure! add the if inside that `

Tarcísio Júnior · Accepted Answer · 2011-10-16 03:53:14Z

22

Something like this that i answer in another question

public class Snippet {
    public static void main(String[] args) {
        int [][]lst = new int[10][10];

        for (int[] arr : lst) {
            System.out.println(Arrays.toString(arr));
        }
    }

}

answered Oct 16, 2011 at 3:53

Tarcísio Júnior

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Comments

kajibu · Accepted Answer · 2018-10-13 09:14:54Z

3

public static void printTwoDimensionalArray(int[][] a) {
    for (int i = 0; i < a.length; i++) {
        for (int j = 0; j < a[i].length; j++) {
            System.out.printf("%d ", a[i][j]);
        }
        System.out.println();
    }
}

just for int array

answered Oct 13, 2018 at 9:14

kajibu

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1 Comment

Michael Kemmerzell Over a year ago

I added a very small improvement: "%d \t".

Wyatt915 · Accepted Answer · 2011-10-17 03:16:07Z

2

Well, since 'X' is a char and not an int, you cannot actually replace it in the matrix itself, however, the following code should print an 'x' char whenever it comes across a 1.

public void printGrid(int[][] in){  
    for(int i = 0; i < 20; i++){  
        for(int j = 0; j < 20; j++){  
            if(in[i][j] == 1)  
                System.out.print('X' + "\t");
            else
                System.out.print(in[i][j] + "\t");
        }
        System.out.print("\n");
    }
}

edited Oct 17, 2011 at 3:16

answered Oct 16, 2011 at 4:25

Wyatt915

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1 Comment

Wyatt915 Over a year ago

This should print just fine. You can add a tab character ("\t", or any character, your preference) at the end of each print statement to separate each element.

jefflunt · Accepted Answer · 2011-10-16 03:05:51Z

1

You should loop by rows and then columns with a structure like

for ...row index...
  for ...column index...
    print

but I guess this is homework so just try it out yourself.

Swap the row/column index in the for loops depending on if you need to go across first and then down, vs. down first and then across.

edited Oct 16, 2011 at 3:05

jefflunt

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answered Oct 16, 2011 at 3:03

Jack

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3 Comments

user997462 Over a year ago

how do I replace the 1 with an x? BTW, not homework...I'm a 40 year old IT pro (networking) who's always been intrigued by programming so learning something new.

Jack Over a year ago

Just check the character on the go (inside the loop) and replace it if it's an '1'

Ted Hopp Over a year ago

@Jack - something like print (a[i][j] == 1 ? 'X' : ' ');

Mykola · Accepted Answer · 2016-03-01 19:09:42Z

1

How about trying this?

public static void main (String [] args)
{
   int [] [] listTwo = new int [5][5];
    // 2 Dimensional array 
    int x = 0;
    int y = 0;
    while (x < 5) {
        listTwo[x][y] = (int)(Math.random()*10);

        while (y <5){
            listTwo [x] [y] = (int)(Math.random()*10);
            System.out.print(listTwo[x][y]+" | ");
            y++;                
        }
        System.out.println("");
        y=0;
        x++;
    }
}

edited Mar 1, 2016 at 19:09

Mykola

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answered Mar 1, 2016 at 18:28

Helvijs

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Comments

ningsuhen · Accepted Answer · 2015-10-15 13:36:12Z

0

If you know the maxValue (can be easily done if another iteration of the elements is not an issue) of the matrix, I find the following code more effective and generic.

    int numDigits = (int) Math.log10(maxValue) + 1;
    if (numDigits <= 1) {
        numDigits = 2;
    }
    StringBuffer buf = new StringBuffer();
    for (int i = 0; i < matrix.length; i++) {
        int[] row = matrix[i];
        for (int j = 0; j < row.length; j++) {
            int block = row[j];
            buf.append(String.format("%" + numDigits + "d", block));
            if (j >= row.length - 1) {
                buf.append("\n");
            }
        }
    }
    return buf.toString();

answered Oct 15, 2015 at 13:36

ningsuhen

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Comments

ChrisHilborne · Accepted Answer · 2020-02-06 22:47:54Z

0

I am also a beginner and I've just managed to crack this using two nested for loops.

I looked at the answers here and tbh they're a bit advanced for me so I thought I'd share mine to help all the other newbies out there.

P.S. It's for a Whack-A-Mole game hence why the array is called 'moleGrid'.

public static void printGrid() {
    for (int i = 0; i < moleGrid.length; i++) {
        for (int j = 0; j < moleGrid[0].length; j++) {
            if (j == 0 || j % (moleGrid.length - 1) != 0) {
                System.out.print(moleGrid[i][j]);
            }
            else {
                System.out.println(moleGrid[i][j]);
            }
         }
     }
}

Hope it helps!

answered Feb 6, 2020 at 22:47

ChrisHilborne

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Comments

Pravin Bansal · Accepted Answer · 2020-08-17 02:19:55Z

0

more simpler approach , use java 5 style for loop

Integer[][] twoDimArray = {{8, 9},{8, 10}};
        for (Integer[] array: twoDimArray){
            System.out.print(array[0] + " ,");
            System.out.println(array[1]);
        }

answered Aug 17, 2020 at 2:19

Pravin Bansal

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