Java根据对象的某个字段排序

古城微笑少年丶 2022-07-11 01:48 250阅读 0赞

正好最近在项目开发中需要对保存在一个List中的对象根据其字段排序，遂总结一下吧，作为一个代码的搬运工，也是需要理解其原理的。

来一个简单的Person类:

public class Person {
        private Long id;
    
        private String name;
    
        public Person(Long id, String name) {
            this.id = id;
            this.name = name;
        }
    
        public Long getId() {
            return id;
        }
    
        public void setId(Long id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public String toString() {
            return "Person{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

现在的需求是根据姓名的拼音首字母进行排序，看代码实现:

@Test
        public void testSort() {
            Person p1 = new Person(1l, "周杰伦");
            Person p2 = new Person(3l, "刘德华");
            Person p3 = new Person(2l, "张学友");
            Person p4 = new Person(4l, "成龙");
            Person p5 = new Person(5l, "胶布虫");
    
            List<Person> persons = Arrays.asList(p1, p2, p3, p4, p5);
    
            Collections.sort(persons, new Comparator<Person>() {
                @Override
                public int compare(Person o1, Person o2) {
                    Collator collator = Collator.getInstance(Locale.CHINA);
                    return collator.compare(o1.getName(), o2.getName());
                }
            });
    
        }

使用Collections.sort方法，传一个Comparator实现类，比较对象字段实现compare方法。

反正我是比较喜欢lambda的写法(使用任何能让我少写代码的方法):

Collections.sort(persons, (o1, o2) -> { Collator collator = Collator.getInstance(Locale.CHINA); return collator.compare(o1.getName(), o2.getName()); }); // another way persons.sort((p1, p2) -> p1.getName.compareTo(p2.getName));

Java中的对象排序都会跟`Comparable` `Comparator` 这两个接口扯上关系，网上已经有很多文章描述了，附文一篇，大家去看吧(实在不想重复造轮子的写，没那个时间):  
[http://www.journaldev.com/780/comparable-and-comparator-in-java-example][http_www.journaldev.com_780_comparable-and-comparator-in-java-example]  
[http://www.importnew.com/15259.html][http_www.importnew.com_15259.html]  
[https://sanaulla.info/2013/03/11/using-lambda-expression-to-sort-a-list-in-java-8-using-netbeans-lambda-support/][https_sanaulla.info_2013_03_11_using-lambda-expression-to-sort-a-list-in-java-8-using-netbeans-lambda-support]

[http_www.journaldev.com_780_comparable-and-comparator-in-java-example]: http://www.journaldev.com/780/comparable-and-comparator-in-java-example
[http_www.importnew.com_15259.html]: http://www.importnew.com/15259.html
[https_sanaulla.info_2013_03_11_using-lambda-expression-to-sort-a-list-in-java-8-using-netbeans-lambda-support]: https://sanaulla.info/2013/03/11/using-lambda-expression-to-sort-a-list-in-java-8-using-netbeans-lambda-support/