计算指定的字符串中出现某一字符串的次数

/**
 * 计算指定的字符串中出现某一字符串的次数
 * 
 */
public class AccountString
{
    
    public static void main(String[] args)
    {
        String str = "rrjavastingjavaabstractjavasunioexcptionjavayy";
        String findStr = "a";
        int count = 0;
        while (str.indexOf(findStr) != -1)
        {
            count++;
            str = str.substring(str.indexOf(findStr) + findStr.length());
        }
        System.out.println("字符串" + findStr + "共出现了" + count + "次!");
    }
}