Format an Integer using Java String Format

Question

I am wondering if it is possible, using the String.format method in Java, to give an integer preceding zeros?

For example:

1 would become 001
2 would become 002
...
11 would become 011
12 would become 012
...
526 would remain as 526
...etc

At the moment I have tried the following code:

String imageName = "_%3d" + "_%s";

for( int i = 0; i < 1000; i++ ){
    System.out.println( String.format( imageName, i, "foo" ) );
}

Unfortunately, this precedes the number with 3 empty spaces. Is it possible to precede the number with zeros instead?

possible duplicate of [Add leading zeroes in Java](http://stackoverflow.com/questions/275711/add-leading-zeroes-in-java) — Jonathon Faust, May 17 '11 at 17:13

score 231 · Answer 1 · edited Sep 15 '19 at 18:19

231

String.format("%03d", 1)  // => "001"
//              │││   └── print the number one
//              ││└────── ... as a decimal integer
//              │└─────── ... minimum of 3 characters wide
//              └──────── ... pad with zeroes instead of spaces

See java.util.Formatter for more information.

edited Sep 15 '19 at 18:19

Basil Bourque

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answered May 17 '11 at 17:16

maerics

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score 179 · Accepted Answer · answered May 17 '11 at 17:13

179

Use %03d in the format specifier for the integer. The 0 means that the number will be zero-filled if it is less than three (in this case) digits.

See the Formatter docs for other modifiers.

answered May 17 '11 at 17:13

Mat

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Anil Bharadia · Answer 3 · 2017-08-01T06:40:58.380

13

If you are using a third party library called apache commons-lang, the following solution can be useful:

Use StringUtils class of apache commons-lang :

int i = 5;
StringUtils.leftPad(String.valueOf(i), 3, "0"); // --> "005"

As StringUtils.leftPad() is faster than String.format()

edited Aug 01 '17 at 06:40

answered Jul 09 '13 at 11:30

Anil Bharadia

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StringUtils.leftPad is another good choice and could be argued that it is more readable plus it allows you to pad with other characters. I have had a Google around but I cannot find anything that confirms it is faster - could you provide some evidence for that? – My Head Hurts Jul 09 '13 at 12:20
https://github.com/anilbharadia/JavaPerformanceTests/blob/master/PerformanceTests/src/org/rw/performance/StringUtilsVsStringFormat.java Run it with junit and check the time – Anil Bharadia Jul 10 '13 at 06:54

Format an Integer using Java String Format

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