Question

How to count the number of non-overlapping instances of substring in a string in Java

Answer 1

public class CountNumberOfNonOverlappingInstancesOfSubstringInAString_Java {
    public static int countOccurrences(String str, String substr) {
        if (substr.isEmpty()) return 0;

        int count = 0;
        int offset = str.indexOf(substr);
        while (offset != -1) {
            count++;
            offset = str.indexOf(substr, offset + substr.length());
        }

        return count;
    }

    public static void main(String[] args) {
        String s = "java php c++ python php phphp";
        
        System.out.println(countOccurrences(s, "php"));
    }
}


   
/*
run:
     
3
    
*/

 

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Answer 2

public class CountNumberOfNonOverlappingInstancesOfSubstringInAString_Java {
    public static void main(String[] args) {
        String s = "java php c++ python php phphp";
        
        System.out.println(countNonOverlappingOccurrences(s, "php"));
    }

    public static int countNonOverlappingOccurrences(String str, String substr) {
        return (str.length() - str.replaceAll("(?i)" + substr, "").length()) / substr.length();
    }
}


   
/*
run:
     
3
    
*/

 

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