java - 如何在纸牌游戏中使用比较器

Question

对于家庭作业，我得到了以下代码，其中方法为空白。我一直在研究它，但我仍然不明白 mutator setComparer 或 Comparator 比较器在这个程序中是如何工作的。我在网上研究了如何使用比较器，但这个想法仍然不清楚。谁能给我一些指导吗？

1. 我必须初始化Comparator比较器吗？如果是这样，我该怎么做？
2. 上面的注释 private int Compare(PlayingCard one, PlayingCard Two) 是什么意思？(this.comparer=null)

谢谢

import java.util.*;
//Class to represent a "generic" hand of playing-cards
public class PlayingCardHand {
//Instance Variables

private int cardsInCompleteHand;     //Maximum # cards in this hand
private ArrayList<PlayingCard> hand; //A hand of Playing-Cards
private Comparator comparer;         //Client-provided comparison of PlayingCards

//Constructor
//Appropriate when PlayingCard compareTo() is to be used to compare PlayingCards
public PlayingCardHand(int handSize) {
    cardsInCompleteHand = handSize;
    hand = new ArrayList<PlayingCard>();

}

//Helper: Compare 2 PlayingCards
// if this.comparer is null, comparison uses compareTo()
//                           otherwise the Comparator is applied
private int compare(PlayingCard one, PlayingCard two) {

    return 0;
}

//Accessor: return # of cards currently in this hand
public int getNumberOfCards() {
    return cardsInCompleteHand;
}

public boolean isComplete() {
    if (hand.size() == cardsInCompleteHand) {
        return true;
    }
    return false;
}

//Accessor: return COPIES of the cards in this hand
public PlayingCard[] getCards() {
    PlayingCard[] temp = new PlayingCard[hand.size()];

    for (int i = 0; i < hand.size(); i++)//ch
    {

        temp[i] = hand.get(i);
    }
    return temp;
}

//Mutator: allows a client to provide a comparison method for PlayingCards
public void setComparer(Comparator comparer) {
}

//Mutator: Append a new card to this hand
public void appendCard(PlayingCard card) {
    int counter = 0;
    PlayingCard.Suit su = card.getSuit();
    PlayingCard.Rank ra = card.getRank();

    PlayingCard temp3 = new PlayingCard(su, ra);

    //10 20 goes here 30 40 if insert 25
    for (int i = 0; i < hand.size(); i++) {
        PlayingCard temp4 = hand.get(i);
        PlayingCard.Suit sui = temp4.getSuit();
        PlayingCard.Rank ran = temp4.getRank();
        if (su.ordinal() <= sui.ordinal() && ra.ordinal() <= ran.ordinal()) {
            hand.add(i, temp3);
            counter++;
        }

    }
    while (counter == 0) {
        hand.add(temp3);
    }
}

Answer 1

基本上，当您想要在相同类型的对象之间进行不同类型的比较时，您可以使用比较器。例如你有

List<Integer> list = new ArrayList<Integer>();

您想要同时进行升序排序和降序排序。你所做的就是编写实现比较器的不同类:

public class Ascending implements Comparator<Integer>{

   @Override
   public int compare(Integer o1, Integer o2) {
       return (o1>o2 ? -1 : (o1==o2 ? 0 : 1));
   }
}
public class Descending implements Comparator<Integer>{

   @Override
   public int compare(Integer o1, Integer o2) {
       return (o1<o2 ? -1 : (o1==o2 ? 0 : 1));
   }
}

然后你可以对数组进行排序:

Collections.sort(list, new Descending());

您问题的答案:

1-这取决于您如何使用 PlayingCardHand 类。据我所知，您需要初始化它。

2- 注释表示使用 PlayingCardHand 的代码将决定使用哪种排序方法。