Java - printing two dimensional array

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...any help would be appreciated.

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

Answers


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();
   }
}

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));

}

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));
        }
    }

}

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.


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");
    }
}

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++;
    }
}

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();

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


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