Using printf() to format output as a grid

Question

I'm trying to grid an output using the printf() statement.

The Strings are generated via a 2D array that is iterated with two for loops

example:

    String[][] arr =
    {
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"}
    }

    for(int i = 0; i < arr.length; i++)
    {
       for(int j = 0; j < arr[0].length; j++)
       {
          System.out.printf("%s", arr[i][j]);
       }
    }

I basically want the output just as it appears in the code (as a 5x5 grid) but the tutorials on formatting are not very easy to follow and most do not deal with this sort of format.

Ideally, the output should look like this:

My question is, besides how would I do this using the printf() characters, is will I come across any problems using these inside a nested for-loop? Also, I understand where the %s comes from, but any further symbol usage is beyond me. Could someone explain why they would use the symbol and characters they are using for this?

Thank you very much.

add System.out.println() after the nested for

Paul Vargas
– Paul Vargas

2012-11-05 17:57:53 +00:00
Commented Nov 5, 2012 at 17:57 — Paul Vargas
– Paul Vargas, Commented Nov 5, 2012 at 17:57

Rohit Jain · Accepted Answer · 2012-11-05 17:57:55Z

2

You need to add a System.out.println(); after your inner loop ends to print your next row in a newline: -

for(int i = 0; i < arr.length; i++)
{
   for(int j = 0; j < arr[0].length; j++)
   {
      System.out.printf("%s ", arr[i][j]);
   }
   System.out.println();
}

For more details on various format specifier see this link: -

http://docs.oracle.com/javase/tutorial/java/data/numberformat.html

answered Nov 5, 2012 at 17:57

Rohit Jain

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3 Comments

Matheus Azevedo Over a year ago

Change System.out.printf("%s", arr[i][j]); to System.out.printf("%s ", arr[i][j]); (space between values)

ATAX Over a year ago

Wow, I had a hunch but I thought I could insert new lines with \n after so many characters. Thank you.

ATAX Over a year ago

Finally got around to choosing this as the accepted answer...2 years later. Sorry about that.

Jeff Ferland · Accepted Answer · 2012-11-05 18:01:20Z

0

Reference for printf() types in Java: http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html

Code:

    for(int i = 0; i < arr.length; i++) {
       for(int j = 0; j < arr[0].length; j++) {
        //System.out.printf("%s", arr[i][j]);
          System.out.printf("%s ", arr[i][j]);
        //The added space will pad the end after each character
       }
       System.out.println();
       //After each pass printing all the characters of your array,
       //this will add a line return.
    }

answered Nov 5, 2012 at 18:01

Jeff Ferland

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Comments

Kumar Vivek Mitra · Accepted Answer · 2012-11-05 18:01:40Z

0

String[][] arr =
    {
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"},
      {"*", "2", "1", "*", "1"}
    }

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

      for(int j=0 ; j<arr.length[i] ; j++){

         System.out.printf("%s ", arr[i][j]);

   }

     System.out.prinln();

}

answered Nov 5, 2012 at 18:01

Kumar Vivek Mitra

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Comments

Scott Wierschem · Accepted Answer · 2017-07-16 21:49:38Z

0

Now that Java 8 has been released, you can use the following:

System.out.printf("%s", Grid.print(width, height, this::showCell));

You'll need to add this as a separate formatter function:

public String showCell(Integer x, Integer y) {
    return arr[x][y];
}

answered Jul 16, 2017 at 21:49

Scott Wierschem

1

Comments

Andronicus · Accepted Answer · 2022-05-12 05:44:23Z

0

I used to make it like this:

for(int i=0;i<matrix.length;i++){
    for(int j=0;j<matrix[i].length;j++){
        System.out.printf("%5d", matrix[i][j]);
    }
    System.out.println(" ");
}

edited May 12, 2022 at 5:44

Andronicus

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answered May 11, 2022 at 18:30

Adrian M

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