Java8 Comparator 排序方法

Posted 2021-12-24 wenqiangit

Java8 Comparator 排序方法

Java8 中 Comparator 接口提供了一些静态方法，可以方便于我们进行排序操作，下面通过例子讲解下如何使用

• 对整数列表排序（升序）

List<Integer> list = Arrays.asList(1, 4, 2, 6, 2, 8);
list.sort(Comparator.naturalOrder());
System.out.println(list);

• 对整数列表排序（降序）

List<Integer> list = Arrays.asList(1, 4, 2, 6, 2, 8);
list.sort(Comparator.reverseOrder());
System.out.println(list);

• 根据对象属性（年龄）进行排序

public class Test 
    public static void main(String[] args) 
        List<Person> personList = new ArrayList<>();
        personList.add(new Person("a", 2));
        personList.add(new Person("b", 4));
        personList.add(new Person("c", 7));
        // 升序
        personList.sort(Comparator.comparingInt(Person::getAge));
        // 降序
        personList.sort(Comparator.comparingInt(Person::getAge).reversed());
        System.out.println(personList);
    

    public static class Person 
        private String name;
        private Integer age;

        public Person(String name, Integer age) 
            this.name = name;
            this.age = age;
        

        public Integer getAge() 
            return age;
        
        
        // ... toString 方法
    

• 根据对象属性（价格、速度）进行排序，需要注意的是，排序有先后之分，不同的顺序会导致不同的结果

public class Test 
    public static void main(String[] args) 
        List<Computer> list = new ArrayList<>();
        list.add(new Computer("xiaomi",4000,6));
        list.add(new Computer("sony",5000,4));
        list.add(new Computer("dell",4000,5));
        list.add(new Computer("mac",6000,8));
        list.add(new Computer("micro",5000,6));
        // 先以价格（升序）、后再速度（升序）
   list.sort(Comparator.comparingInt(Computer::getPrice).thenComparingInt(Computer::getSpeed));
        // 先以速度（降序）、后再价格（升序）
     list.sort(Comparator.comparingInt(Computer::getSpeed).reversed().thenComparingInt(Computer::getPrice));
        // 先以价格（降序）、后再速度（降序）
        list.sort(Comparator.comparingInt(Computer::getPrice).thenComparingInt(Computer::getSpeed).reversed());
        System.out.println(list);
    

    public static class Computer 
        private String name;
        private Integer price;
        private Integer speed;

        public Computer(String name, Integer price, Integer speed) 
            this.name = name;
            this.price = price;
            this.speed = speed;
        

        public Integer getPrice() 

            return price;
        

        public void setPrice(Integer price) 
            this.price = price;
        

        public Integer getSpeed() 
            return speed;
        

        public void setSpeed(Integer speed) 
            this.speed = speed;
        

        // ... toString 方法