public void testSortString() {
        List<String> stringList = new ArrayList<>();
        /*随机生成10条字符串*/
        String s;
        for (int i = 0; i < 10; i++) {
            do{
//              s = randomString();/*字符串随机方法1*/
                s = stringRandom();/*字符串随机方法2(推荐)*/
            }while(stringList.contains(s));
            stringList.add(s);
            System.out.println("成功添加字符串：" + s);
        }
        System.out.println("-----------Before Sort------------");
        for (String string : stringList) {
            System.out.println("元素：" + string);
        }
        Collections.sort(stringList);
        System.out.println("-----------After Sort------------");
        for (String string : stringList) {
            System.out.println("元素：" + string);
        }
    }

    /*字符串随机方法1*/
    public String  randomString(){
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        char[] A_a_0 = {'A','a','0'};
        Integer charRadom;  // 字符数组A_a_0下标
        Integer stringLength;//字符串长度 1~10
        Integer numRandom;//数字随机范围 0~9
        Integer letterRandom;//字母随机范围 0~25
        /*防止出现长度为0的情况*/
        do {
            stringLength = random.nextInt(10);
        } while (stringLength == 0);    
        for (int i = 1; i <= stringLength; i++) {
            char c;
                        /*字符数组A_a_0下标随机，0~2*/
            charRadom = random.nextInt(3);
                        /*数字的情况*/
            if (charRadom == 2) {
                numRandom = random.nextInt(10);//数字随机范围 0~9
                                /*将 ‘0’ 的ASCII码值 加上 随机数，并强转为字符*/
                c = (char) (A_a_0[charRadom] + numRandom);
                sb.append(c);
            }else{ // 字母的情况
                 letterRandom = random.nextInt(26);//字母随机范围 0~25
                                /*将 ‘a’ 或 'A' 的ASCII码值 加上 随机数，并强转为字符*/
                 c = (char) (A_a_0[charRadom] + letterRandom);
                 sb.append(c);
            }
        }
        return sb.toString();
    }

        /*字符串随机方法2（推荐）*/
    public String stringRandom() {
        StringBuilder sb = new StringBuilder();
        String s = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        char[] c = s.toCharArray();//将字符串转化为字符数组
        Random random = new Random();
        Integer length ;//字符串长度
        Integer charRandom;//字符数组c下标随机
        /*防止出现长度为0的情况*/
        do {
            length = random.nextInt(10);
        } while (length == 0);  
        for (int i = 1; i <= length; i++) {
            charRandom = random.nextInt(c.length);
            sb.append(c[charRandom]);
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        CollectionsTest ct = new CollectionsTest();
        ct.testSortString();
    }