随机生成char数组，没有重复的索引

Question

想要在char数组中生成没有重复索引的随机字符，并将它们存储在新的ArrayList中。

ArrayList<Character> al = new ArrayList<>();

char letters[ ] = {'a', 'b', 'c', 'd', 'e'};

for(int i =0; i<letters.length; i++){

    al.add(letters[ i ]);

}

ArrayList<Character> al2 = new ArrayList<>();

Random random = new Random ();

while (al.size() > 0) {

    int randomizedNumber = random.nextInt(al.size());

    al2.add(letters[ randomizedNumber ]; //adding randomized charterer in the new ArrayList.

    al.remove(letters[ randomizedNumber ];

}