Java-如何检查数组的值是否包含指定值作为属性

Question

我有一个Player对象数组。播放器具有名称，当我添加播放器时，我想检查播放器名称是否已经存在。以下代码永远不会引发异常，它只会添加重复的播放器。

public void addPlayer(String name, boolean gender, int index)  throws RuntimeException {
    List<String> names = new ArrayList<>();

    if (names.contains(name))
        throw new DuplicatePlayerException();
    else {
        players[index] = new Player(name, gender);
        names.add(name);
    }
}

Answer 1

public void addPlayer(String name, boolean gender, int index)  throws RuntimeException {
    List<String> names = new ArrayList<>(); // you create a new instance of the list each time you call it, so it'll always be empty

    if (names.contains(name)) // your empty list does not contain anything
        throw new DuplicatePlayerException();
    else {
        players[index] = new Player(name, gender);
        names.add(name);
    }
}

您需要更改方法，以使用实例级别列表：

private List<String> names = new ArrayList<>();
public void addPlayer(String name, boolean gender, int index)  throws RuntimeException {
    if (names.contains(name))
        throw new DuplicatePlayerException();
    else {
        players[index] = new Player(name, gender);
        names.add(name);
    }
}

因此，names您每次调用方法时都不会删除的内容。