匿名内部类

    /*
         * 把一个字符串内的内容进行字典顺序排序，并不去重复
         */
    
        String string = "asdiaaa";
        char[] ch = string.toCharArray();
        //创建集合对象
        TreeSet<Character> t = new TreeSet<>(new Comparator<Character>() {
            @Override
            //匿名内部类，进行排序，并不删除
            public int compare(Character o1, Character o2) {
                int num = o1.compareTo(o2);
                return num == 0 ? 1 : num;
            }
        });
        
        //添加元素到集合
        for (int i = 0; i < ch.length; i++) {
            char c = ch[i];
            t.add(c);
        }
        //遍历输出
        for (Character character : t) {
            System.out.print(character + " ");
        }