List集合中的对象进行排序

    public  class A  implements Comparable<A>{
        private Integer id;
        private String name;

        public A(){
        }
        public A(Integer id , String name){
            this.id = id;
            this.name = name;
        }

        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        @Override
        public String toString(){
            return "id:" + id + ";name:" + name;
        }

        @Override
        public int compareTo(A o) {
            //正序
            return o.getId().compareTo(this.getId());
            //倒序
            //return this.getId().compareTo(o.getId());
        }
    }
    public  class A  implements