Need to split a string into two parts in java

Question

I have a string which contains a contiguous chunk of digits and then a contiguous chunk of characters. I need to split them into two parts (one integer part, and one string)

Answer 1

Use lookarounds: str.split("(?<=\\d)(?=\\D)")

String[] parts = "123XYZ".split("(?<=\\d)(?=\\D)");
System.out.println(parts[0] + "-" + parts[1]);
// prints "123-XYZ"

\d is the character class for digits; \D is its negation. So this zero-matching assertion matches the position where the preceding character is a digit (?<=\d), and the following character is a non-digit (?=\D).

References

• regular-expressions.info/Lookarounds and Character Class

Related questions

• Java split is eating my characters.
• Is there a way to split strings with String.split() and include the delimiters?

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Alternate solution using limited split

The following also works:

    String[] parts = "123XYZ".split("(?=\\D)", 2);
    System.out.println(parts[0] + "-" + parts[1]);

This splits just before we see a non-digit. This is much closer to your original solution, except that since it doesn't actually match the non-digit character, it doesn't "eat it up". Also, it uses limit of 2, which is really what you want here.

API links

• String.split(String regex, int limit)
  • If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter.

Answer 2

There's always an old-fashioned way:

private String[] split(String in) {    
  int indexOfFirstChar = 0;
  for (char c : in.toCharArray()) {
    if (Character.isDigit(c)) {
      indexOfFirstChar++;
    } else {
      break;
    } 
  }    
  return new String[]{in.substring(0,indexOfFirstChar), in.substring(indexOfFirstChar)};
}

(hope it works with digit-only or char-only Strings too - can't test it here - if not, take it as a general idea)