通过在内部 class 中实现 Comparable 来提供多种排序选项

Question

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

如何访问内部 class 中被覆盖的 compareTo 方法？我想使用 inner classes 因为一旦按名字排序有效，我将创建 inner classes 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

class compareFirstName

class compareFirstName implements Comparator<Person>{
@override
public int compareTo(Person p1,Person p2){
return p1.getFirstName().compareTo(p2.getFirstName());
}
}

在你的 main 方法上创建上面的实例 class 并使用 Collections class 来排序

compareFirstName c = new compareFirstName ();
List<Person> yourPersonList = new ArrayList<>();
.........................
Collections.sort(yourPersonList, c);
for(Person p : yourPersonList) {
  System.out.println(p.getFirstName()+","+p.getLastName()+","+p.getAge());
}

通过在内部 class 中实现 Comparable 来提供多种排序选项

Providing multiple sort options by implementing Comparable in inner class

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