public static void main(String[] args) {
		// TODO Auto-generated method stub
		//1.键盘接收
         Scanner sc = new Scanner(System.in);
         System.out.println("请输入一个字符串:");
         String lineStr = sc.nextLine();
         //2.将字符串转化成字符数组
         char[] strArr = lineStr.toCharArray();
         //3.定义TreeSet集合，传入比较器对字符排序并保留重复
         TreeSet<Character> ts = new TreeSet<>(new Comparator<Character>(){
			@Override
			public int compare(Character o1, Character o2) {
				int num = o1-o2;   //自动拆箱 也可以写成 int num = o1.compareTo(o2)
				return num == 0?1:num;
			}
         });
         //4.遍历字符数组,将每一个字符存储在TreeSet集合中
         for (char obj : strArr) {
			ts.add(obj); //自动装箱
		}
         //5.遍历TreeSet集合，打印每一个字符
         for (Character str : ts) {
			System.out.print(str);
		}
	}

}