当有奇数队号时，我的夹具算法会抛出异常

Question

当团队列表计数为奇数时，我的夹具生成器算法会抛出 java.lang.IndexOutOfBoundsException。我正在发送 21 个大小的团队列表并给出了这个例外。即使是 17、19、23 也会抛出相同的异常。这是异常：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.xelorium.soccerleaguetable, PID: 1189
java.lang.IndexOutOfBoundsException: Index: 21, Size: 21
    at java.util.LinkedList.checkElementIndex(LinkedList.java:555)
    at java.util.LinkedList.get(LinkedList.java:476)
    at com.xelorium.soccerleaguetable.FixtureGenerator.getFixtures(FixtureGenerator.java:34)

FixtureGenerator.java:

public class FixtureGenerator<T extends Object> {

public List<List<MatchModel<T>>> getFixtures(List<T> teams, boolean includeReverseFixtures) {

    int numberOfTeams = teams.size();

    boolean ghost = false;
    if (numberOfTeams % 2 != 0) {
        numberOfTeams++;
        ghost = true;
    }

    int totalRounds = numberOfTeams - 1;
    int matchesPerRound = numberOfTeams / 2;
    List<List<MatchModel<T>>> rounds = new LinkedList<List<MatchModel<T>>>();

    for (int round = 0; round < totalRounds; round++) {
        List<MatchModel<T>> fixtures = new LinkedList<MatchModel<T>>();
        for (int match = 0; match < matchesPerRound; match++) {
            int home = (round + match) % (numberOfTeams - 1);
            int away = (numberOfTeams - 1 - match + round) % (numberOfTeams - 1);

            if (match == 0) {
                away = numberOfTeams - 1;
            }
            //Here where it throws the exception
            fixtures.add(new MatchModel<T>(teams.get(home), teams.get(away)));
        }
        rounds.add(fixtures);
    }

Answer 1

在这里，您要增加团队数量并尝试匹配一个甚至不存在的团队。

if (numberOfTeams % 2 != 0) {
    numberOfTeams++;
    ghost = true;
}

假设您有 21 个团队，团队列表中的最后一个索引是 20（索引从零开始）。但是“numberOfTeams”是 22。在这个 if 块中，“away”将是 22 - 1 = 21，然后尝试到达列表中的 21st 索引团队。但是这个团队不存在。

if (match == 0) {
    away = numberOfTeams - 1;
}

//Here where it throws the exception
fixtures.add(new MatchModel<T>(teams.get(home), teams.get(away)));

作为一种解决方案，当团队数量为奇数时，您可以将空团队添加到绕过列表。

当有奇数队号时，我的夹具算法会抛出异常

My fixture algorithm throws exception when there are odd team numbers

java

algorithm

exception

fixtures