对具有多个字段的arrayList进行排序

Question

我有一个 Gift 类型的数组列表 每个 Present 对象都有字段 String name, String type , double Cost

我想找到一种使用每个礼物的成本对 arrayList 进行排序的方法

我使用的语言是 Java

请问我该怎么做

Answer 1

我想找到一种使用每个礼物的成本对 arrayList 进行排序的方法

您需要：

1. 在您的自定义 Present 类中实现 Comparable
2. 创建一个自定义 Comparator 以与 Collection.sort(...) 方法一起使用

这是我的例子，展示了这两种方法：

/*
**  Use the Collections API to sort a List for you.
**
**  When your class has a "natural" sort order you can implement
**  the Comparable interface.
**
**  You can use an alternate sort order when you implement
**  a Comparator for your class.
*/
import java.util.*;

public class Person implements Comparable<Person>
{
    String name;
    int age;

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

    public String getName()
    {
        return name;
    }

    public int getAge()
    {
        return age;
    }

    public String toString()
    {
        return name + " : " + age;
    }

    /*
    **  Implement the natural order for this class
    */
    public int compareTo(Person p)
    {
        return getName().compareTo(p.getName());
    }

    static class AgeComparator implements Comparator<Person>
    {
        public int compare(Person p1, Person p2)
        {
            return p1.getAge() - p2.getAge();
        }
    }

    public static void main(String[] args)
    {
        List<Person> people = new ArrayList<Person>();
        people.add( new Person("Homer", 38) );
        people.add( new Person("Marge", 35) );
        people.add( new Person("Bart", 15) );
        people.add( new Person("Lisa", 13) );

        // Sort by natural order

        Collections.sort(people);
        System.out.println("Sort by Natural order");
        System.out.println("\t" + people);

        // Sort by reverse natural order

        Collections.sort(people, Collections.reverseOrder());
        System.out.println("Sort by reverse natural order");
        System.out.println("\t" + people);

        //  Use a Comparator to sort by age

        Collections.sort(people, new Person.AgeComparator());
        System.out.println("Sort using Age Comparator");
        System.out.println("\t" + people);

        //  Use a Comparator to sort by descending age

        Collections.sort(people, Collections.reverseOrder(new Person.AgeComparator()));
        System.out.println("Sort using Reverse Age Comparator");
        System.out.println("\t" + people);
    }
}

Answer 2

你看过类似的界面吗？ http://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html?

也许看看下面的问题，看看如何实现这个interface. https://stackoverflow.com/questions/3718383/java-class-implements-comparable

Answer 3

您可以使用Comparable or Comparator。在您的情况下，Comparable 更可取。