随机字符串

public void testSort3(){
        //随机十个字符串段，
        //每个字符串段都不相同
        //每个字符串段的位数也不相同
        //重新排列字符串段
        List<String> zifuList = new ArrayList<String>();//创建一个新的集合对象
        char[] zf = {'a','b','c','d','e','f','d','h','i','j','k','l','m','n','o','p',
                     'q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G'
                    ,'H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X'
                    ,'Y','Z','0','1','2','3','4','5','6','7','8','9','@','$'};//包含足够的字符
        Random random = new Random();//创建一个随机数,

        for(int j = 0;j<10;j++){
            String U= new String();
            do{
                for(int i=0;i<random.nextInt(zf.length)+1;i++){
                    U += String.valueOf(zf[random.nextInt(zf.length)]);
                    }   
               }while(zifuList.contains(U));
            zifuList.add(U);
            System.out.println("已添加元素："+U);
            }   

        System.out.println("***********排序前***************");
        for(String ss:zifuList){
            System.out.println(ss);
        }

        Collections.sort(zifuList);
        System.out.println("***********排序后前***************");
        for(String ss:zifuList){
            System.out.println(ss);
        }
    }
    public void testRandom(){
     Random rm = new Random();
     for(int k=0;k<10;k++){
         System.out.println(rm.nextInt(10));
        }   
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        CollectionsTest cl = new CollectionsTest();
        cl.testSort3();
        //cl.testRandom();
    }