某笔试题（一）获取20个随机不重复的字符

import java.util.ArrayList;import java.util.Random;public class sort {public static void main(String[] args){System.out.println(get());}public static ArrayList<Character> get(){ArrayList<Character> list = new ArrayList<>(20);while(list.size() <= 20){//1.获取随机字符cchar c = getRandomCharacter();//2.比较，ArrayList的indexOf方法是真的方便if (list.indexOf(c) == -1) {list.add(c);}}return list;}//获取1-20的随机数public static char getRandomCharacter(){String base = "qwertyuioplkjhgfdsazxcvbnm";return base.charAt(new Random().nextInt(26));}}