Customer has a problem with formatted output. He wants to write a VERY
simple program. Read doubles from file, and print these doubles
and their square roots to an output file, neatly formatted into
two columns (with a blank between) where each double takes 8
characters, i.e. 5 positions for integer part, 1 for decimal
point, and 2 for fractional part:


The input file
- - - - - - -
   1.1
  22.2
 333.3
4444.4


Desired output file, "line format" is "iiiii.ff iiiii.ff"
- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    1.10 1.05
   22.20 4.71
  333.30 18.26
 4444.40 66.67


Below, is enclosed a (working) C program, and a vain attempt to
write a Java program that does the same thing:
 

The corresponding C program
- - - - - - - - - - - - - -
#include <stdio.h>
#include <math.h>

main() {
    FILE *fip; /* Input file */
    FILE *fop; /* Output file */
    char buf[256]; /* Input file line */
    double x;

    fip = fopen("testin.txt", "r");
    fop = fopen("testout.txt", "w");
    while (fgets(buf, 255, fip)) {
        sscanf(buf, "%lf", &x);
        fprintf(fop, "%8.2lf %8.2lf\n", x, sqrt(x));
    }
    fclose(fip);
    fclose(fop);
}


The C output file (which is exactly what I want)
- - - - - - - - - - - - - - - - - - - - - - - -
    1.10 1.05
   22.20 4.71
  333.30 18.26
 4444.40 66.67


The Java program
- - - - - - - -
import java.io.*;
import java.text.*;

class Test {
    public static void main(String args[]) throws IOException {
        java.util.Locale.setDefault(java.util.Locale.ENGLISH);

        FileInputStream is = new FileInputStream("testin.txt");
        FileOutputStream os = new FileOutputStream("testout.txt");
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        PrintWriter pw = new PrintWriter(os);

        DecimalFormat df = new DecimalFormat("####0.00"); // *** PATTERN ***

        for (String s = br.readLine(); s != null; s = br.readLine()) {
            double x = Double.parseDouble(s);
            pw.println(df.format(x)+" "+df.format(Math.sqrt(x)));
        }

        is.close();
        pw.flush();
        os.close();
    }
}


Try 1. Java output file, if I use DecimalFormat pattern "####0.00":
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1.10 1.05
22.20 4.71
333.30 18.26
4444.40 66.67


Try 2. Java output file, if I use DecimalFormat pattern "00000.00":
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
00001.10 00001.05
00022.20 00004.71
00333.30 00018.26
04444.40 00066.67


Try 3. Java output file, if I use DecimalFormat pattern " 0.00":
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    1.10 1.05
    22.20 4.71
    333.30 18.26
    4444.40 66.67


Desired output file; is this really IMPOSSIBLE to get?
- - - - - - - - - - - - - - - - - - - - - - - - - - -
    1.10 1.05
   22.20 4.71
  333.30 18.26
 4444.40 66.67


There should be a simple DecimalFormat formatting character that
says "pad to a fixed width replacing leading zeros with spaces".
-- linden@eng, June 21 1999