java-list排序

代码

@Test
    void sort05(){
    
    
        List<Integer> list = new ArrayList<Integer>();
        list.add(new Integer(5));
        list.add(new Integer(13));
        list.add(new Integer(4));
        list.add(new Integer(9));
        Collections.sort(list);
        System.out.println(list.toString());

        //对数字进行排序
        List<Integer> nums = Arrays.asList(3,1,5,2,9,8,4,10,6,7);
        nums.sort(Comparator.reverseOrder()); //reverseOrder倒序
        System.err.println("倒序:"+nums);

        nums.sort(Comparator.naturalOrder()); //naturalOrder自然排序即：正序
        System.err.println("正序:"+nums);

        User user0 = new User(1,"jack","6");
        User user1 = new User(1,"jack","9");
        User user2 = new User(1,"jack","5");
        User user3 = new User(1,"jack","3");
        ArrayList<User> users = new ArrayList<>();
        users.add(user0);
        users.add(user1);
        users.add(user2);
        users.add(user3);
       // users.sort((o1, o2)->o1.getPassword().compareTo(o2.getPassword()));
        //users.sort(Comparator.comparing(User::getPassword));
        //第六写法,个Lambda写法，JAVA8的写法
        Comparator<User> ageComparator = (o1, o2)->o1.getPassword().compareTo(o2.getPassword());
        //users.sort(ageComparator);       //按上面配置的顺序取值
        users.sort(ageComparator.reversed());    //按上面配置的顺序反向取值
        for (User u:users) {
    
    
            System.out.println(u);
        }
    }

参考文章

https://my.oschina.net/sdlvzg/blog/2243766

对象List单属性排序

List<Developer> listDevs = ComparatorTest.getDevelopers();

System.out.println("排序前:");
//JAVA8的写法，循环
listDevs.forEach((developer)->System.out.println(developer));

//第一个写法
Collections.sort(listDevs, new Comparator<Developer>() {
    
    
    @Override
    public int compare(Developer o1, Developer o2) {
    
    
        return o1.getAge().compareTo(o2.getAge());
    }
});
//第二个写法,JAVA8的写法，List 接口支持直接使用 sort 该方法，不再需要使用 Collections.sort 了
//listDevs.sort(listDevs, new Comparator<Developer>() {
    
    
//   @Override
//   public int compare(Developer o1, Developer o2) {
    
    
//       return o1.getAge().compareTo(o2.getAge();
//   }
//});

//第三个写法,Lambda写法，JAVA8的写法
//listDevs.sort((Developer o1, Developer o2)->o1.getAge().compareTo(o2.getAge()));

//第四个写法,Lambda写法，JAVA8的写法
//listDevs.sort((o1, o2)->o1.getAge().compareTo(o2.getAge()));

//第五写法,个Lambda写法，JAVA8的写法
//listDevs.sort(Comparator.comparing(Developer::getAge));

//第六写法,个Lambda写法，JAVA8的写法
Comparator<Developer> ageComparator = (o1, o2)->o1.getAge().compareTo(o2.getAge());
listDevs.sort(ageComparator);       //按上面配置的顺序取值
listDevs.sort(ageComparator.reversed());    //按上面配置的顺序反向取值

System.out.println("排序后:");
//JAVA8的写法，循环
listDevs.forEach((developer)->System.out.println(developer));