java中Collections.sort() 排序函数的用法

用Collections.sort方法对list排序有两种方法
第一种是list中的对象实现Comparable接口，如下：

/**

* 根据order对User排序*/public class User implements Comparable<User>{    private String name;    private Integer order;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getOrder() {        return order;    }    public void setOrder(Integer order) {        this.order = order;    }    public int compareTo(User arg0) {        return this.getOrder().compareTo(arg0.getOrder());    }}

测试一下：
public class Test{    public static void main(String[] args) {        User user1 = new User();        user1.setName("a");        user1.setOrder(1);        User user2 = new User();        user2.setName("b");        user2.setOrder(2);        List<User> list = new ArrayList<User>();        //此处add user2再add user1        list.add(user2);        list.add(user1);        Collections.sort(list);        for(User u : list){            System.out.println(u.getName());        }    }}

输出结果如下
a
b
第二种方法是根据Collections.sort重载方法来实现，例如：输出结果如下
/*** 根据order对User排序*/public class User { //此处无需实现Comparable接口    private String name;    private Integer order;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getOrder() {        return order;    }    public void setOrder(Integer order) {        this.order = order;    }}主类中这样写即可：public class Test{    public static void main(String[] args) {        User user1 = new User();        user1.setName("a");        user1.setOrder(1);        User user2 = new User();        user2.setName("b");        user2.setOrder(2);        List<User> list = new ArrayList<User>();        list.add(user2);        list.add(user1);               Collections.sort(list,new Comparator<User>(){            public int compare(User arg0, User arg1) {                return arg0.getOrder().compareTo(arg1.getOrder());            }        });        for(User u : list){            System.out.println(u.getName());        }    }}