Java集合排序（面试必考点之一）

public class Person implements Comparable<Person> {
    private int age;

    private String name;

    public int getAge() {
        return age;
    }

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

    public String getName() {
        return name;
    }

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

    public Person(int age, String name) {
        super();
        this.age = age;
        this.name = name;
    }

    @Override
    public int compareTo(Person o) {
        if (this.age > o.age) {
            return 1;
        } else if (this.age < o.age) {
            return -1;
        } else {
            return 0;
        }
    }

    public static void main(String[] args) {
        List<Person> pList = new ArrayList<>();
        Person p1 = new Person(10, "a张三");
        Person p2 = new Person(18, "c李四");
        Person p3 = new Person(20, "b王五");
        Person p4 = new Person(15, "d陈六");
        pList.add(p1);
        pList.add(p2);
        pList.add(p3);
        pList.add(p4);

        System.out.println("排序前依次输出：");
        for (Person p : pList) {
            System.out.println(p.age + "===" + p.name);
        }

        // 按照年龄升序排序（默认）
        Collections.sort(pList);

        System.out.println("按年龄升序排序后依次输出：");
        for (Person p : pList) {
            System.out.println(p.age + "===" + p.name);
        }

        // 按照年龄倒叙排序
        Collections.reverse(pList);

        System.out.println("按年龄倒叙排序后依次输出：");
        for (Person p : pList) {
            System.out.println(p.age + "===" + p.name);
        }

        // 按照姓名升序排序
        Collections.sort(pList, new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                return o1.getName().compareTo(o2.getName());
            }
        });

        System.out.println("按照姓名升序排序后依次输出：");
        for (Person p : pList) {
            System.out.println(p.age + "===" + p.name);
        }

    }
}