给一串字符串，打乱字符串顺序

import ;

public class Pratice {
    //给一串字符串，打乱字符串顺序
    //修改字符串有两个思路
    //
    //2.字符数组
    public static void main(String[] args) {
        String str="abcdefg";

        char arr[]=();
        Random random=new Random();
        for (int i = 0; i < ; i++) {
            int a = (0, );
            char temp = arr[i];
            arr[i] = arr[a];
            arr[a] = temp;
        }
        String result=new String(arr);

        (result);
    }

}