How to remove leading zeros from alphanumeric text?

Question

I've seen questions on how to prefix zeros here in SO. But not the other way!

Can you guys suggest me how to remove the leading zeros in alphanumeric text? Are there any built-in APIs or do I need to write a method to trim the leading zeros?

Example:

01234 converts to 1234

0001234a converts to 1234a

001234-a converts to 1234-a

101234 remains as 101234

2509398 remains as 2509398

123z remains as 123z

000002829839 converts to 2829839

Answer 1

Regex is the most useful tool for the job; what it should depend on the problem specification. The following extracts leading zeroes but leave one if necessary (i.e. it wouldn't really turn "0" to a blank string).

s.replaceFirst("^0+(?!$)", "")

The ^ anchor will make sure that the 0+ being coordinated is at the beginning of the input. The (?!$) negative lookahead guarantees that not the entire string will be matched.

Test harness:

String[] in = {

    "01234", // "[1234]"

    "0001234a", // "[1234a]"

    "101234", // "[101234]"

    "000002829839", // "[2829839]"

    "0", // "[0]"

    "0000000", // "[0]"

    "0000009", // "[9]"

    "000000z", // "[z]"

    "000000.z", // "[.z]"

};

for (String s : in) {

    System.out.println("[" + s.replaceFirst("^0+(?!$)", "") + "]");

}

Check:

• regular-expressions.info
  • repetitions, lookarounds, and anchors
• String.replaceFirst(String regex)