Question

How to remove the last n occurrences of a substring in a string in Java

Answer 1

import java.util.ArrayList;
import java.util.List;

public class RemoveLastN {

    // Remove last n occurrences of substring
    public static String removeLastN(String s, String sub, int n) {
        List<Integer> positions = new ArrayList<>();
        int pos = s.indexOf(sub);

        // Find all occurrences
        while (pos != -1) {
            positions.add(pos);
            pos = s.indexOf(sub, pos + sub.length());
        }

        // Remove from the end
        StringBuilder sb = new StringBuilder(s);
        for (int i = positions.size() - 1; i >= 0 && n > 0; i--, n--) {
            int start = positions.get(i);
            sb.delete(start, start + sub.length());
        }

        return sb.toString();
    }

    // Remove extra spaces (collapse multiple spaces, trim ends)
    public static String removeExtraSpaces(String s) {
        String[] parts = s.trim().split("\\s+");
        return String.join(" ", parts);
    }

    public static void main(String[] args) {
        String text = "abc xyz xyz abc xyzabcxyz abc";

        String result = removeLastN(text, "xyz", 3);
        System.out.println(result);

        String cleaned = removeExtraSpaces(result);
        System.out.println(cleaned);
    }
}



/*
run:

abc xyz  abc abc abc
abc xyz abc abc abc

*/

 

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