Shuffle the characters of a string in Java

This is a program which accepts a string using the BufferdReader and InputStreamReader class, and then shuffle the characters present inside the string and generate a new string which is displayed in the console. Basically the characters of the string are stored in a Character List using the for each loop. Then the characters in that list is randomly removed and appended in a StringBuilder object output.

Screenshots [Demo]

The Code:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
class Brain
{
 public static void main(String []as)throws IOException
 {
  BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  System.out.print("Enter The String: ");
  String input=br.readLine();
  List<Character> characters = new ArrayList<Character>();
        for(char c:input.toCharArray()){
            characters.add(c);
        }
        StringBuilder output = new StringBuilder(input.length());
        while(characters.size()!=0){
            int randPicker = (int)(Math.random()*characters.size());
            output.append(characters.remove(randPicker));
        }
        System.out.println("THe Shuffled is : "+output.toString());
 }
}