java - 如何使索引小于大小

Question

我无法让索引小于 arrayList 的大小，以便我可以发牌。这是我的代码:

import java.util.Collection;
import java.util.Collections;
import java.util.Random;
import java.util.ArrayList;

public class Deck {
   ArrayList<Card> unusedCards = new ArrayList<Card>();
   ArrayList<Card> usedCards = new ArrayList<Card>();
   Card newCard = new Card();
   Random rand = new Random();


//Creates a Deck of 52 randomly ordered card objects (No repeats)
public Deck() {
     for (int i = 0; i <= 52; i++) {
         while (unusedCards.contains(newCard)) {
             newCard = new Card();
         }
         unusedCards.add(newCard);
     }
}
//shuffles the arraylist of the deck of cards, making it so the cards are dealt in a different order
public void shuffle(){
    Collections.shuffle(unusedCards);
}

//Boolean is true when the Unsed deck has no cards left
public boolean isEmpty(){
    if (unusedCards.size() == 0) return true;
    else return false;
}

//returns an arraylist containing the specified number of cards
public ArrayList<Card> Deal(int numToDeal){
    ArrayList<Card> DealCards = new ArrayList<Card>();

    for (int i = 0; i < numToDeal; i++){
        int index = rand.nextInt(50);
        DealCards.add(unusedCards.get(index));
        usedCards.add(unusedCards.get(index));
        unusedCards.remove(unusedCards.get(index));
        }

    return DealCards;
}

}

当我尝试发多张牌时，我不断收到此错误:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 48, Size: 48
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at nnajiO.Deck.Deal(Deck.java:41)
at nnajiO.CrazyEights.main(CrazyEights.java:26)

如果您能提供帮助，谢谢。

Answer 1

您将 53 张牌放入牌堆中。

for (int i = 0; i <= 52; i++) {

数组中索引的范围是0 .. length-1 。因此您想使用<上述语句中的运算符而不是 <=运算符。

另一个问题类似。您正在从 unusedCards 中删除卡片使用静态随机范围时:

int index = rand.nextInt(50);

在这种情况下，应该更改为以下内容，以避免选择超出范围的索引:

int index = rand.nextInt(unusedCards.size());