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?

Answer 1

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.

Answer 2

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.

Answer 3

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()