CountMatches.java

public class CountMatches{

     public static void main(String []args){
        int c = CountMatches.countMatches("abcabdabdab", "abdab");
        System.out.println(String.format("Count: %d", c ));
     }
     
      public static int countMatches(String str, String sub) {
        if (isEmpty(str) || isEmpty(sub)) {
            return 0;
        }
        int count = 0;
        int idx = 0;
        while ((idx = str.indexOf(sub, idx)) != -1) {
            count++;
            idx += sub.length();
        }
        return count;
    }
        public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }

}