public static void countSubstring(){
        //方法1：遍歷法
        String s1="abcdabc";
        String s2="ab";
        int count=0;
        for(int i=0;s1.indexOf(s2)!=-1;i++){
            count++;
            s1=s1.substring(s1.indexOf(s2)+s2.length());
        }
        System.out.println(count); //2

        //方法2：分割法
 

        s1="abcdabc";
        String[] arr=s1.split(s2);
        int len=arr.length-1;
        if(s1.endsWith(s2)) len++;
        System.out.println(len); //2
    }