I've checked my script on some test data and it works fine.
package pl.codegym.task.task19.task1907;
/*
Liczenie słów
*/
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Collections;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
String fileName = bf.readLine();
bf.close();
BufferedReader bufferedReader = new BufferedReader(new FileReader(fileName));
StringBuilder stringBuilder = new StringBuilder();
while (bufferedReader.ready()) {
stringBuilder.append(bufferedReader.readLine());
}
bufferedReader.close();
String[] parts = stringBuilder.toString().replaceAll("[.,-_;:]", " ").split(" ");
System.out.println(Collections.frequency(Arrays.asList(parts), "świat"));
}
}