通过在内部类中实现 Comparable 来提供多种排序选项

Question

我有一个人员对象的数组列表，每个对象都有名字、姓氏和年龄。我想使用内部类提供一种按名字对这些对象进行排序的方法。

我如何访问内部类中重写的compareTo方法？我想使用内部类，因为一旦按名字排序起作用，我将创建内部类以按其他属性排序。

package listdemo;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class ListDemo {

    public static void main(String[] args) {

        List<Person> people = new ArrayList<>();

        people.add(new Person("Homer", "Simpson", 29));

        people.add(new Person("Mo", "Sizlak", 23));

        people.add(new Person("Bart", "Simpson", 22));

        people.add(new Person("Peter", "Griffin", 30));

        people.add(new Person("Joe", "Swanson", 27));

    }

}

package listdemo;

public class Person {

    private String firstName;

    private String lastName;

    private int age;

    public Person(String firstName, String lastName, int age) {

        this.firstName = firstName;

        this.lastName = lastName;

        this.age = age;

        //create an instance of the inner class upon initialization of Person

        Person.CompareFirstName compareFirstName = this.new CompareFirstName();

    }

    public String getFirstName() {

        return firstName;

    }

    public void setFirstName(String firstName) {

        this.firstName = firstName;

    }

    public String getLastName() {

        return lastName;

    }

    public void setLastName(String lastName) {

        this.lastName = lastName;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    @Override

    public String toString() {

        return this.firstName + " " + this.lastName + " " +  this.age;

    }

    class CompareFirstName implements Comparable<Person> {

        @Override

        public int compareTo(Person comparePerson) {

            System.out.println("inner class compareTo method invoked");

            int difference = Person.this.firstName.compareTo(comparePerson.getFirstName());

            return difference;

        }

    }

}

Answer 1

类比较名字class compareFirstName implements Comparator<Person>{@overridepublic int compareTo(Person p1,Person p2){return p1.getFirstName().compareTo(p2.getFirstName());}}在您的主要方法上创建上述类的实例并使用 Collections 类进行排序compareFirstName c = new compareFirstName ();List<Person> yourPersonList = new ArrayList<>();.........................Collections.sort(yourPersonList, c);for(Person p : yourPersonList) {&nbsp; System.out.println(p.getFirstName()+","+p.getLastName()+","+p.getAge());}