CODEWITHSUNDEEP
javaformattingprintf
Chris Conway
Chris Conway

Reputation: 55989

Java: Print a 2D String array as a right-justified table

What is the best way to print the cells of a String[][] array as a right-justified table? For example, the input

{ { "x", "xxx" }, { "yyy", "y" }, { "zz", "zz" } }

should yield the output

  x xxx
yyy   y
 zz  zz

This seems like something that one should be able to accomplish using java.util.Formatter, but it doesn't seem to allow non-constant field widths. The best answer will use some standard method for padding the table cells, not the manual insertion of space characters.

Upvotes: 3

Views: 15363

Answers (3)

Chris Conway
Chris Conway

Reputation: 55989

Here's an answer, using dynamically-generated format strings for each column:

public static void printTable(String[][] table) {
  // Find out what the maximum number of columns is in any row
  int maxColumns = 0;
  for (int i = 0; i < table.length; i++) {
    maxColumns = Math.max(table[i].length, maxColumns);
  }

  // Find the maximum length of a string in each column
  int[] lengths = new int[maxColumns];
  for (int i = 0; i < table.length; i++) {
    for (int j = 0; j < table[i].length; j++) {
      lengths[j] = Math.max(table[i][j].length(), lengths[j]);
    }
  }

  // Generate a format string for each column
  String[] formats = new String[lengths.length];
  for (int i = 0; i < lengths.length; i++) {
   formats[i] = "%1$" + lengths[i] + "s" 
       + (i + 1 == lengths.length ? "\n" : " ");
 }

  // Print 'em out
  for (int i = 0; i < table.length; i++) {
    for (int j = 0; j < table[i].length; j++) {
      System.out.printf(formats[j], table[i][j]);
    }
  }
}

Upvotes: 8

PhiLho
PhiLho

Reputation: 41142

Indeed, if you specify a width for the fields, it should be right-justified.
If you need to have a dynamic padding, minimal for the longest string, you have to walk the array, getting the maximal width, generate the format string with the width computed from this maxima, and use it for format the output.

Upvotes: 4

Aditya Mukherji
Aditya Mukherji

Reputation: 9256

find the length of the longest string..
left pad all the strings with spaces until they r that length + 1
System.out.print them using 2 nested for loops

Upvotes: 1

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