Finding second occurrence of a substring in a string in Java

Question

We are given a string, say, "itiswhatitis" and a substring, say, "is". I need to find the index of 'i' when the string "is" occurs a second time in the original string.

String.indexOf("is") will return 2 in this case. I want the output to be 10 in this case.

Solution 1

Use overloaded version of indexOf(), which takes the starting index (fromIndex) as 2nd parameter:

str.indexOf("is", str.indexOf("is") + 1);

Solution 2

I am using: Apache Commons Lang: StringUtils.ordinalIndexOf()

StringUtils.ordinalIndexOf("Java Language", "a", 2)

Solution 3

int first = string.indexOf("is");
int second = string.indexOf("is", first + 1);

This overload starts looking for the substring from the given index.

Solution 4

You can write a function to return array of occurrence positions, Java has String.regionMatches function which is quite handy

public static ArrayList<Integer> occurrencesPos(String str, String substr) {
    final boolean ignoreCase = true;
    int substrLength = substr.length();
    int strLength = str.length();

    ArrayList<Integer> occurrenceArr = new ArrayList<Integer>();

    for(int i = 0; i < strLength - substrLength + 1; i++) {
        if(str.regionMatches(ignoreCase, i, substr, 0, substrLength))  {
            occurrenceArr.add(i);
        }
    }
    return occurrenceArr;
}

Solution 5

I hope I'm not late to the party.. Here is my answer. I like using Pattern/Matcher because it uses regex which should be more efficient. Yet, I think this answer could be enhanced:

    Matcher matcher = Pattern.compile("is").matcher("I think there is a smarter solution, isn't there?");
    int numOfOcurrences = 2;
    for(int i = 0; i < numOfOcurrences; i++) matcher.find();
    System.out.println("Index: " + matcher.start());

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Comments

[Pravat Panda]

what if the occurence is more than twice?

[Jeroen Vannevel]

Then nothing special happens, it will still take the second occurence.

[Pravat Panda]

what about the index of third occurence!

[Jeroen Vannevel]

What about it? The question was to find the second occurence.

[Pravat Panda]

i mean what if 10 occcurences are there in the string

[Juha Untinen]

@PravatPanda: I guess you want to know how to get the third occurence? Then you could just continue the code in Jeroen's answer and add a third string.indexOf("is", second + 1); although it would probably be better to make a method that returns the Nth indexOf

[Pravat Panda]

@JuhaUntinen recursion??

[sofs1]

This is ingenious.

[Hassan Jamil]

Nice solution, I found. Thank you Hasnaa!

[Osmar]

Nice and clear, thanks!