collections.sort对javabean的list

1、collection.sort排序

算法底层实际是 将集合转换成array，再执行arrays.sort，arrays.sort利用归并排序，优化的快排，timSort等方式。

2、对string类型数据排序

public static void collectionSort() {                List unSorted = new ArrayList();                unSorted.add("10");                unSorted.add("99");                unSorted.add("21");                Collections.sort(unSorted);                for(String a:unSorted) {                        System.out.print(a +"  ");                }        }

输出：10 21 99

3、对javabean类型数据排序

（1）方式一

import java.io.Serializable;public class unSortedBean implements Serializable{        private static final long serialVersionUID = 1L;                private String name;        private String age;        private int order;        public String getName() {                return name;        }        public void setName(String name) {                this.name = name;        }        public String getAge() {                return age;        }        public void setAge(String age) {                this.age = age;        }        public int getOrder() {                return order;        }        public void setOrder(int order) {                this.order = order;        }}

以下为排序代码，编译期就报错：

public static void javaBeanSort() {                List unSorted = new ArrayList();                unSortedBean a1 = new unSortedBean();                a1.setName("张三");                a1.setAge("24");                a1.setOrder(9);                unSorted.add(a1);                unSortedBean a2 = new unSortedBean();                a2.setName("李四");                a2.setAge("22");                a2.setOrder(5);                unSorted.add(a2);                unSortedBean a3 = new unSortedBean();                a3.setName("王五");                a3.setAge("36");                a3.setOrder(10);                unSorted.add(a3);                Collections.sort(unSorted);        }

原因：string实现了comparable接口，而自定义的javabean未实现，可以用这种方式排序

Collections.sort(unSorted,new Comparator() {                        @Override                        public int compare(unSortedBean arg0, unSortedBean arg1) {                                // 升叙                                return arg0.getOrder()-arg1.getOrder();                        }                });                for(unSortedBean bean:unSorted) {                        System.out.print(JSONObject.fromObject(bean));                }

输出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","age":"24"}{"order":10,"name":"王五","age":"36"}

（2）方式二

也可以用collections.sort();方式，只需要javabean实现comparable接口

import java.io.Serializable;public class unSortedBean implements Serializable, Comparable{        private static final long serialVersionUID = 1L;                private String name;        private String age;        private int order;        public String getName() {                return name;        }        public void setName(String name) {                this.name = name;        }        public String getAge() {                return age;        }        public void setAge(String age) {                this.age = age;        }                public int getOrder() {                return order;        }        public void setOrder(int order) {                this.order = order;        }        @Override        public int compareTo(unSortedBean arg0) {                // TODO 升叙                return this.order-arg0.getOrder();        }        }

输出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","age":"24"}{"order":10,"name":"王五","age":"36"}

注意：如果order是string型数字，需要转换成数字型再比较，否则比较结果可能不是预期效果。

比如把本文中的order全部换成string型，输出结果为

{"order":10,"name":"王五","age":"36"}{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","age":"24"}