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

问题

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.

回答1:

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.

回答2:

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]);
    }
  }
}

回答3:

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

来源：https://stackoverflow.com/questions/275338/java-print-a-2d-string-array-as-a-right-justified-table

标签

java

formatting

printf