【Java】【Stream流】排序

使用Java提供的流API提升代码质量，此次分享排序

先上示例代码，如下

import lombok.Data;

@Data
public class User {
    private String name;
    private Integer age;
    private Integer schoolNumber;
}

写一个main，需求：按照年龄，由低到高排序

public class SortDemo {
    public static void main(String[] args) {
        List<User> list = new ArrayList<>();
        User user1 = new User();
        User user2 = new User();
        User user3 = new User();
        user1.setAge(18);
        user2.setAge(16);
        user3.setAge(17);
        user1.setName("人物1");
        user2.setName("人物2");
        user3.setName("人物3");
        user1.setSchoolNumber(88);
        user2.setSchoolNumber(99);
        user3.setSchoolNumber(100);


        list.add(user1);
        list.add(user2);
        list.add(user3);
        //需求：按照年龄，由低到高排序(默认即是顺序排序)
        List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge))
                .collect(Collectors.toList());
        users.forEach(System.out::println);
    }
}

结果如下图：

需求2：按照年龄倒叙排序

List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge,Comparator.reverseOrder()))
                .collect(Collectors.toList());
        users.forEach(System.out::println);

结果如下图：

需求3：按照年龄、学号排序

List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge)
                        .thenComparing(User::getSchoolNumber))
                .collect(Collectors.toList());

结果如下图：

需求4：按照年龄倒叙、学号排序

List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge,Comparator.reverseOrder())
                        .thenComparing(User::getSchoolNumber))
                .collect(Collectors.toList());

结果如下图：

需求5：按照年龄倒叙、学号倒叙 排序

List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge,Comparator.reverseOrder())
                        .thenComparing(User::getSchoolNumber,Comparator.reverseOrder()))
                .collect(Collectors.toList());

结果如下图：

最后，对结果先排序，最后分页

List<User> users = list.stream()
                .sorted(Comparator.comparing(User::getAge,Comparator.reverseOrder())
                        .thenComparing(User::getSchoolNumber,Comparator.reverseOrder()))
                .skip((long)((currentPage - 1) * pageSize))
                .limit(pageSize)
                .collect(Collectors.toList());