public class Demo5 {
    public static void main(String []args) {
        int count=0; //统计
        int index=0;  //索引
        String s="ALDFJKaaLDANLFaa aadasfaaa";
        String s2="aa";
        while((index = s.indexOf(s2))!= -1) {  //-1为 没有找到
        count++;
        s=s.substring(index+s2.length()); //s.substring(9)
        }
        System.out.print(count);
    }
}