public static int countString(String minstr,String maxstr){

    int len1 = minstr.length();

    int count = 0;

    int index = maxstr.indexOf(minstr);

    while(index != -1){

    count++;

    maxstr = maxstr.substring(index + len1,maxstr.length());

    index = maxstr.indexOf(minstr);

    }

    return count;

    }

改进

while((index = maxstr.indexOf(minstr,maxstr)) != -1){

   count++;

   index = maxstr.indexOf(minstr);

 }

return count;