java - How to format the printing of doubles

Question

Im making a division table from 1-10 an the results range from integers to x.x to x.xx i used decimalformat to keep the the numbers to 2 decimal places but that throws off the format of the table. How would i print the numbers so that they would all be x.xx

for example
1 -> 1.00
0.5 -> 0.50
0.333... -> 0.33

DecimalFormat df = new DecimalFormat("#.##");
System.out.println("     1       2       3       4       5       6       7       8       9       10");
for(double i=1;i<=10;i++){
  System.out.print(df.format(i)+"  ");
  if (i<10) System.out.print(" ");
  else System.out.print("");
  for(double j=1;j<=10;j++){
    double div=(j/i);
    System.out.print(df.format(div));
    if (div < 10) System.out.print("   ");
  }
  System.out.println();

this prints
   1      2      3      4      5      6      7      8      9      10
1   1   2   3   4   5   6   7   8   9   10
2   0.5   1   1.5   2   2.5   3   3.5   4   4.5   5   
3   0.33   0.67   1   1.33   1.67   2   2.33   2.67   3   3.33   
4   0.25   0.5   0.75   1   1.25   1.5   1.75   2   2.25   2.5   
5   0.2   0.4   0.6   0.8   1   1.2   1.4   1.6   1.8   2   
6   0.17   0.33   0.5   0.67   0.83   1   1.17   1.33   1.5   1.67   
7   0.14   0.29   0.43   0.57   0.71   0.86   1   1.14   1.29   1.43   
8   0.12   0.25   0.38   0.5   0.62   0.75   0.88   1   1.12   1.25   
9   0.11   0.22   0.33   0.44   0.56   0.67   0.78   0.89   1   1.11   
10  0.1   0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1   

i want to print everything as x.xx or neatly in columns 
1 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00  10.0
2 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50  5.00
3 0.33 0.67 1.00 1.33 1.67 2.00 2.33 2.67 3.00  3.33
etc

Answer 1

Many ways, but one is to use String.format("%.2f", myDouble) Another way is to use a DecimalFormat such as DecimalFormat format = new DecimalFormat("#0.00") and then use it like format.format(myDouble)

To format a table, use String.format(...) or one of its variants like printf.

e.g.

public class Foo2 {
   private static final int COLS = 10;
   private static final int ROWS = 10;

   public static void main(String[] args) {
      System.out.printf("%2s", "");
      for (int i = 0; i < COLS; i++) {
         System.out.printf("%8d", (i + 1));
      }
      System.out.println();
      for (int i = 0; i < ROWS; i++) {
         int row = i + 1;
         System.out.printf("%2d", row);
         for (int j = 0; j < ROWS; j++) {
            double myDouble = (double) row / (j + 1);
            System.out.printf("%8.2f", myDouble);
         }
         System.out.println();
      }
   }
}

which prints out

         1       2       3       4       5       6       7       8       9      10
 1    1.00    0.50    0.33    0.25    0.20    0.17    0.14    0.13    0.11    0.10
 2    2.00    1.00    0.67    0.50    0.40    0.33    0.29    0.25    0.22    0.20
 3    3.00    1.50    1.00    0.75    0.60    0.50    0.43    0.38    0.33    0.30
 4    4.00    2.00    1.33    1.00    0.80    0.67    0.57    0.50    0.44    0.40
 5    5.00    2.50    1.67    1.25    1.00    0.83    0.71    0.63    0.56    0.50
 6    6.00    3.00    2.00    1.50    1.20    1.00    0.86    0.75    0.67    0.60
 7    7.00    3.50    2.33    1.75    1.40    1.17    1.00    0.88    0.78    0.70
 8    8.00    4.00    2.67    2.00    1.60    1.33    1.14    1.00    0.89    0.80
 9    9.00    4.50    3.00    2.25    1.80    1.50    1.29    1.13    1.00    0.90
10   10.00    5.00    3.33    2.50    2.00    1.67    1.43    1.25    1.11    1.00