How many subStrings Java implenmentation

I. Question

Given a string s1 and another string substr, count how many substr in s.

For example: s1: helloworldhello substr : llo return 2.

II. Idea

First, find the index of substr from s1, cut the head of s1 which contains first substr(length need to cut = index + substr.length). And then find the index of substr from rest part, and repeat

III. Java implenmentation

package org.lovian.string;

/**
 * How many substrings
 *
 * @author PENG Zhengshuai
 * @lovian.org
 *
 */
public class HowManySubStr {
	public static int countSubString(String originalStr, String subStr) {
		int count = 0;
		String tmp = originalStr;
		int index = tmp.indexOf(subStr);
		while (index != -1) {	//if index = -1, means substr doesn't exist
			count++;
			tmp = tmp.substring(index + subStr.length());	//rest part of string
			index = tmp.indexOf(subStr);
		}
		return count;
	}

	public static void main(String[] args) {

		String s1 = "woaijavawoaijavawozhendeaijavawotaiaijavale";
		String subStr = "java";
		System.out.println("count: " + countSubString(s1, subStr));
		;
	}
}

result:

count: 4
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