Java入门第三季的作业-随机字符串排序

看了众多幕友的代码，实在脑洞大开，牛到爆炸，还是要多学习啊....
思考了许久，贴上核心代码希望能跟大家一起交流！

public void testSort3(){
        List<String> stringList=new ArrayList<String>();
        String st="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        Random random=new Random();
        for(int k=1;k<=10;k++){
            StringBuilder zy= new StringBuilder();
            int j=random.nextInt(10)+1;
            do {
                for(int i=1;i<=j;i++){
                zy.append(st.charAt(random.nextInt(st.length())));  
                }
            }while(stringList.contains(zy));
            stringList.add(zy.toString());
        }
        System.out.println("------------排序前------------");
        for (String string : stringList) {
            System.out.println("元素："+string);
        }
        Collections.sort(stringList);
        System.out.println("------------排序后------------");
        for (String string : stringList) {
            System.out.println("元素："+string);
            }   
        }