How to find nth occurrence of character in a string?

java string substring
Gnanam picture Gnanam · Oct 20, 2010 · Viewed 186.7k times · Source

Similar to a question posted here, am looking for a solution in Java.

That is, how to find the index of nth occurrence of a character/string from a string?

Example: "/folder1/folder2/folder3/". In this case, if I ask for 3rd occurrence of slash (/), it appears before folder3, and I expect to return this index position. My actual intention is to substring it from nth occurrence of a character.

Is there any convenient/ready-to-use method available in Java API or do we need to write a small logic on our own to solve this?

Also,

  1. I quickly searched whether any method is supported for this purpose at Apache Commons Lang's StringUtils, but I don't find any.
  2. Can regular expressions help in this regard?

Answer

aioobe picture aioobe · Oct 20, 2010

If your project already depends on Apache Commons you can use StringUtils.ordinalIndexOf, otherwise, here's an implementation:

public static int ordinalIndexOf(String str, String substr, int n) {
    int pos = str.indexOf(substr);
    while (--n > 0 && pos != -1)
        pos = str.indexOf(substr, pos + 1);
    return pos;
}

This post has been rewritten as an article here.

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