需求: person(id,name,age) 设计一个可扩展的可根据id，name，age正序倒序排序；如果name/age相同,按id的正序排序；

• Person.java

/**
 * 实体类
 * @Author dabai
 * @Date 2019-08-28
 */
public class Person {

    private int id;

    private String name;

    private int age;

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

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

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

• Sorter接口

/**
 * 策略接口
 * @Author dabai
 * @Date 2019-08-28
 */
public interface Sorter<T> {

    /**
     * 根据传入参数list和比较器 排序
     * @param list
     * @param comparator
     */
    void sort(List<T> list, Comparator<T> comparator);

    /**
     * 获取自然序比较器
     * @return
     */
    Comparator<T> getAscComparator();

    /**
     * 获取倒序比较器
     * @return
     */
    Comparator<T> getDescComparator();
}

• AbstractSorter.java

/**
 * @Author dabai
 * @Date 2019-08-28
 */
public abstract class AbstractSorter<T> implements Sorter<T> {


    @Override
    public void sort(List<T> list, Comparator<T> comparator) {
        list.sort(list,comparator);
    }
}

• IDSorter.java

/**
 * id 排序策略
 * @Author dabai
 * @Date 2019-08-28
 */
public class IDSorter extends AbstractSorter<Person> {

    @Override
    public Comparator<Person> getAscComparator() {
        return Comparator.comparingInt(Person::getId);
    }

    @Override
    public Comparator<Person> getDescComparator() {
        return Comparator.comparingInt(Person::getId).reversed();
    }
}

• NameSorter.java

/**
 * @Author dabai
 * @Date 2019-08-28
 */
public class NameSorter extends AbstractSorter<Person> {


    @Override
    public Comparator<Person> getAscComparator() {
        return (o1, o2) -> {
            if (o1.getName().compareToIgnoreCase(o2.getName()) == 0) {
                return o1.getId() - o2.getId();
            }
            return o1.getName().compareToIgnoreCase(o2.getName());
        };
    }

    @Override
    public Comparator<Person> getDescComparator() {
        return (o1, o2) -> {
            if (o1.getName().compareToIgnoreCase(o2.getName()) == 0) {
                return o1.getId() - o2.getId();
            }
            return o2.getName().compareToIgnoreCase(o1.getName());
        };
    }
}

• AgeSorter.java

/**
 * @Author dabai
 * @Date 2019-08-28
 */
public class AgeSorter extends AbstractSorter<Person> {


    @Override
    public Comparator<Person> getAscComparator() {
        return (o1, o2) -> {
            if (o1.getAge() == o2.getAge()) {
                return o1.getId() - o2.getId();
            }
            return o1.getAge() - o2.getAge();
        };
    }

    @Override
    public Comparator<Person> getDescComparator() {
        return (o1, o2) -> {
            if (o1.getAge() == o2.getAge()) {
                return o1.getId() - o2.getId();
            }
            return o2.getAge() - o1.getAge();
        };
    }
}

• Client.java

/**
 * @Author dabai
 * @Date 2019-08-28
 */
public class Client {

    public static void main(String[] args) {

        // 1. 组装数据
        Person p1 = new Person(1, "dabai", 30);
        Person p2 = new Person(2, "baye", 30);
        Person p3 = new Person(10, "wangwu", 25);
        Person p4 = new Person(9, "dabai", 30);
        Person p5 = new Person(6, "zhaoliu", 50);
        Person p6 = new Person(3, "lisi", 30);
        Person p7 = new Person(4, "qinyao", 39);

        List<Person> personList = Arrays.asList(p1, p2, p3, p4, p5, p6, p7);


        // 2. 获取环境单例
        Enviroment env = Enviroment.getInstance();

        // 3. ID策略 并 调用
        IDSorter idSorter = new IDSorter();
        env.sort(personList, idSorter);
        env.sort(personList, idSorter, false);

        // 4. Name策略 并 调用
        NameSorter nameSorter = new NameSorter();
        env.sort(personList, nameSorter);
        env.sort(personList, nameSorter, false);


        // 5. Age策略 并 调用
        AgeSorter ageSorter = new AgeSorter();
        env.sort(personList, ageSorter);
        env.sort(personList, ageSorter, false);

        // 6. 遍历输出排序后的数据
        personList.forEach(System.out::println);
    }
}