如何在java中查找子串的计数

public class SubstringCountExample {
    public static void main(String[] args) {
        String str = "hello world, hello universe";
        String subStr = "hello";
        int count = str.split(subStr).length - 1;
        System.out.println("子串 \"" + subStr + "\" 出现的次数: " + count);
    }
}

public class SubstringCountExample {
    public static void main(String[] args) {
        String str = "hello world, hello universe";
        String subStr = "hello";
        int count = 0;
        int index = 0;
        while ((index = str.indexOf(subStr, index)) != -1) {
            count++;
            index += subStr.length();
        }
        System.out.println("子串 \"" + subStr + "\" 出现的次数: " + count);
    }
}

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class SubstringCountExample {
    public static void main(String[] args) {
        String str = "hello world, hello universe";
        String subStr = "hello";
        Pattern pattern = Pattern.compile(subStr);
        Matcher matcher = pattern.matcher(str);
        int count = 0;
        while (matcher.find()) {
            count++;
        }
        System.out.println("子串 \"" + subStr + "\" 出现的次数: " + count);
    }
}