对List集合中的对象进行按某个属性排序

实现效果

编写代码

1、实体类对象实现Comparable接口重写compareTo方法

public class User implements Comparable<User>{
    private String name;
    private Integer age;

    public User() {
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public int compareTo(User o) {
        return this.age.compareTo(o.getAge());
    }
}

2、使用demo

public class ListBySort {
    public static void main(String[] args) {
        List<User> list=new ArrayList<>();
        User user = new User("张三",19);
        list.add(user);
        User user1 = new User("李四",20);
        list.add(user1);
        User user2 = new User("王五",16);
        list.add(user2);

        System.out.println("升序排序前:"+list);
        Collections.sort(list, new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
                return o1.getAge().compareTo(o2.getAge());
            }
        });
        System.out.println("升序排序后:"+list);
        Collections.sort(list, new Comparator<User>() {
            @Override
            public int compare(User o1, User o2) {
                return o2.getAge().compareTo(o1.getAge());
            }
        });
        System.out.println("降序排序后:"+list);
    }
}

Java8之后使用stream().sorted()排序

同样需要对实体对象实现Comparable接口重写compareTo方法

使用同样的测试数据

public class ListByStream {
    public static void main(String[] args) {
        List<User> list=new ArrayList<>();
        User user = new User("张三",19,175);
        list.add(user);
        User user1 = new User("李四",20,177);
        list.add(user1);
        User user2 = new User("王五",16,180);
        list.add(user2);
        User user3 = new User("赵六",16,170);
        list.add(user3);


        System.out.println("升序排序前:"+list);
        List<User> collect = list.stream().sorted(Comparator.comparing(User::getAge)).collect(Collectors.toList());
        System.out.println("升序排序后:"+collect);
        List<User> collect1 = list.stream().sorted(Comparator.comparing(User::getAge).reversed()).collect(Collectors.toList());
        System.out.println("降序排序后:"+collect1);
        //对相同的年龄再次按照升高排序
        List<User> collect2 = list.stream()
                .sorted(Comparator.comparing(User::getAge).reversed().thenComparing(User::getHeight))
                .collect(Collectors.toList());
        System.out.println("降序排序后再对升高升序排序:"+collect2);
    }
}

参考文章：

1.https://www.cnblogs.com/wdzhz/p/11583359.html
2.https://www.cnblogs.com/codecat/p/10873757.html