Java - Write code to count Matches in a string

Requirements

Write code to count Matches in a string

Demo

//package com.book2s;

public class Main {
    public static void main(String[] argv) {
        String str = "book2s.com";
        String subStr = "book2s.com";
        System.out.println(countMatches(str, subStr));
    }/* www.  j  a v  a2  s.com*/

    public static int countMatches(String str, String subStr) {
        if ((str == null) || (str.length() == 0) || (subStr == null)
                || (subStr.length() == 0)) {
            return 0;
        }

        int count = 0;
        int index = 0;

        while ((index = str.indexOf(subStr, index)) != -1) {
            count++;
            index += subStr.length();
        }

        return count;
    }

}