Беда

if (s.trim().equals("world"))

while (bufferedReader1.ready()){
            listStr.add(bufferedReader1.readLine());
        }

public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String readerFile = bufferedReader.readLine();
        BufferedReader  bufferedReader1 = new BufferedReader(new FileReader(readerFile));
        ArrayList<String> listStr = new ArrayList<>();
        while (bufferedReader1.ready()){
            listStr.add(bufferedReader1.readLine());
        }
        int count = 0;
        for (String string : listStr) {
            String[] str = string.split("\\p{Punct}");
            for (String s : str) {
                if (s.trim().equals("world"))
                    count++;
            }
        }
        System.out.println(count);
        bufferedReader.close();
        bufferedReader1.close();
    }

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
String readerFile = bufferedReader.readLine();
bufferedReader = new BufferedReader(new FileReader(readerFile));

String s = "";
while (bufferedReader.ready()){
    s = s + (char)bufferedReader.read();
}
//System.out.println(s); для проверки программмы, можно удалить эту строку
String[] str = s.split("world");
System.out.println(str.length-1);
bufferedReader.close();

флоыврофлworld,awjheajkworld,worldasdjakl,world

Pattern pattern = Pattern.compile("\\w+", Pattern.UNICODE_CHARACTER_CLASS
                | Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(file);
ArrayList<String> list = new ArrayList<>();

while (matcher.find())
    list.add(matcher.group().toLowerCase());
int count = 0;
for (String word : list) if(word.equals("world")) count++;
System.out.println(count);

list.add(matcher.group().toLowerCase());