How to set width AND pad integer witdth String Formatter in Java

Question

Given I have the following integers:

1, 10, 100

I want to pad them with zeroes to have exactly 3 digits:

001
010
100

and I want to print them prefixed by 10 spaces:

      001 //assume 10 spaces from the beginning of the line 
      010
      100

I want to use Java formatter string to accomplish this but am only successful in accomplishing one of the above mention conditions but not both at once.

Below are 2 expressions that I created that accomplish each one of these conditions:

    @Test
    public void test1() {

        String[] langs = { "TEXTX", "TEXTXXX", "TEXTXX" };
        int[] nums = {1, 10, 100};

        for (int i = 0; i < 3; i++) {

            String s = langs[i];
            int n = nums[i];

            System.out.printf("%1$s%2$14s%3$03d\n", s, " ", n);
        }

    }

According to documentation the formatter string has the below form:

%[argument_index$][flags][width][.precision]conversion

but apparently the zero padding flag parameter cannot be followed by width parameter as it is being parsed as one number resulting in a "long width".

How can this be rewritten to accomplish the above mentioned conditions?

NOTE:

My only idea was to explicitly add a single space to the arguments and try to manipulate it as an argument. Something like this:

System.out.printf("%1$s%2$10s%3$03d\n", s, " ", n);

EDIT:

My apologies, I just realized that I didn't fully described my question. These numbers need to follow certain other strings of different length, like this:

textX       001
textXXX     010
textXX      100

So that the spacing is variable.

Are all the number being printed <= 999? If so, you could just prefix it with fixed 10-spaces string... — Jiri Tousek
– Jiri Tousek, Commented Jul 7, 2017 at 7:27
Do you want to pad to length 10 with spaces or just add 10 spaces to the front as @Jiri suggested? — Tim Biegeleisen
– Tim Biegeleisen, Commented Jul 7, 2017 at 7:29
From the update it looks like you're trying to use variable padding on the second column to pad different sizes of the first column. — Jiri Tousek
– Jiri Tousek, Commented Jul 7, 2017 at 7:40

msfoster · Accepted Answer · 2017-07-07 08:23:11Z

7

If the two only criterias are the padding of 10 Spaces and zero-padding of the numbers:

final String str = String.format("%10s%03d", " ", 2);

Edit after update from OP:

 System.out.printf("%-10s%03d", "abc", 2);

How it Works:

We need two arguments for Our pattern, one for the String of length 10, and one for the integer.

%10s is a pattern for a String of length 10. In order to left align it, we add the -: %-10s. The second argument is the integer of length 3 that we want to left pad With zero: %03d.

If we dont want to rearrange or reuse an argument for multiple format specifiers, just pass the arguments in the order specified in the pattern.

edited Jul 7, 2017 at 8:23

answered Jul 7, 2017 at 7:31

msfoster

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4 Comments

Eugene S Over a year ago

Spot on! Thanks so much. Based on my understanding of the formatter string syntax it looks like you used 2 formatter strings together? So the - gets it left justified to the beginning of the string, not the previous character as I thought.

Eugene S Over a year ago

Actually looking at it again, I am not sure how it works. Could you please briefly explain? It looks like you are setting the width to the string (%-10s) and not to the integer. Also don't you need to use argument_index$ to point to each argument?

msfoster Over a year ago

I've added some description. Yes, the Width is set individually for the String and integer.

Eugene S Over a year ago

Thanks for adding the explanation!

Tim Biegeleisen · Accepted Answer · 2017-07-07 07:41:17Z

0

This answer is based on your latest edit, which revealed this data:

textX       001
textXXX     010
textXX      100

Assuming that the second column always has a width of 3, then your problem distills down to figuring out how many spaces need to be added after the first text column. Here is how you could do this in Java 7:

String text = "textXXX";
int n = 10 - text.length();
String padding = String.format("%0" + n + "d", 0).replace("0", " ");

In Java 8 you could this to get the padding string:

String padding = String.join("", Collections.nCopies(n, " "));

answered Jul 7, 2017 at 7:41

Tim Biegeleisen

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