Add leading zeroes to a string

Question

I want to add some leading zeroes to a string, the total length must be eight characters. For example:

123 should be 00000123
1243 should be 00001234
123456 should be 00123456
12345678 should be 12345678

What's the easiest way?

You seem to mean "leading zeroes", not trailing. – Henry Keiter Jun 13 '13 at 22:37 — Henry Keiter, Jun 13 '13 at 22:37

score 36 · Answer 1 · answered Jun 13 '13 at 22:36

36

A cheesy little trick

String str = "123";
String formatted = ("00000000" + str).substring(str.length())

If you started with a number instead:

Int number = 123;
String formatted = String.format("%08d", number);

answered Jun 13 '13 at 22:36

Jean-Bernard Pellerin

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the cheesy little trick is worth remembering for lots of different languages - sql dialects you don't use often for example – Levin Magruder Nov 26 '13 at 18:09
1

The first example is nice at first but it breaks if the original number is longer than 8 digits. Furthermore, if you do `("00000000" + number)` with number being an integer or long it will provide you with a string as a result. But the second option will be safer. – pablisco Aug 13 '14 at 09:54

fge · Answer 2 · 2013-06-13T22:44:57.287

30

Use String.format(), it has a specifier for that already:

String.format("%08d", myInteger);

More generally, see the javadoc for Formatter. It has a lot of neat stuff -- more than you can see at a first glance.

edited Jun 13 '13 at 22:44

answered Jun 13 '13 at 22:38

fge

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It wouldn't work with strings because the padding will be spaces. – Jean-Bernard Pellerin Jun 13 '13 at 22:42
Well, yeah, OK, not exactly like it does for numbers – fge Jun 13 '13 at 22:42
Bingo. That is exactly what I need. – ncmathsadist Jan 18 '16 at 19:36

score 10 · Answer 3 · answered Oct 17 '16 at 14:35

10

Using apache common langs lib:

StringUtils.leftPad(str, 8, '0');

answered Oct 17 '16 at 14:35

Andrey Sarul

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score 7 · Answer 4 · answered Mar 09 '16 at 23:08

Using `DecimalFormat`:

static public void main(String[] args) {
    int vals[] = {123, 1243, 123456, 12345678};
    DecimalFormat decimalFormat = new DecimalFormat("00000000");
    for (int val : vals) {
        System.out.println(decimalFormat.format(val));
    }
}

Output:

Mr. Polywhirl · Answer 5 · 2013-06-14T00:01:49.430

4

Why not make a simple padding function? I know there are libraries, but this is a very simple task.

System.out.println(padStr(123, "0", 8));
System.out.println(padStr(1234, "0", 8));
System.out.println(padStr(123456, "0", 8));
System.out.println(padStr(12345678, "0", 8));       

public String padStr(int val, String pad, int len) {
  String str = Integer.toString(val);
  while (str.length() < len)
    str = pad + str;
  return str;
}

edited Jun 14 '13 at 00:01

answered Jun 13 '13 at 23:56

Mr. Polywhirl

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This will produce a new StringBuilder and a new String on every iteration of the loop. – whiskeysierra Oct 17 '16 at 11:04

score 1 · Answer 6 · answered Jul 24 '14 at 10:36

public static void main(String[] args)
{
    String stringForTest = "123";
    int requiredLengthAfterPadding = 8;
    int inputStringLengh = stringForTest.length();
    int diff = requiredLengthAfterPadding - inputStringLengh;
    if (inputStringLengh < requiredLengthAfterPadding)
    {
        stringForTest = new String(new char[diff]).replace("\0", "0")+ stringForTest;
    }
    System.out.println(stringForTest);
}

Add leading zeroes to a string

6 Answers6

Using `DecimalFormat`:

Linked

Related

Add leading zeroes to a string

6 Answers6

Using DecimalFormat:

Linked

Related

Using `DecimalFormat`: