01.01. Is Unique LCCI

class Solution {
    public boolean isUnique(String astr) {
        char[] str = astr.toCharArray();
        Arrays.sort(str);
        boolean flag = true;
        for(int i=0;i){
            if(str[i]==str[i+1]){
                return false;
            }
        }

        return true;


    }
}