java - 从地图中检索第一个和第二个值

Question

从地图中获取第一个值和第二个值的最佳方法是什么。我正在尝试阅读tableLists地图并first and second value从地图中获取。

下面是我ReadTableConnectionInfo的类代码。

private final LinkedHashMap<String, ReadTableConnectionInfo> tableLists;

ReadTableConnectionInfo table = tablePicker();


private ReadTableConnectionInfo tablePicker() {

    Random r = new SecureRandom();
    ReadTableConnectionInfo table;

    if (r.nextFloat() < Read.percentageTable / 100) {
        table = get first value from tableLists map
    } else {
        table = get second value from tableLists map
    }

    return table;
}

Answer 1

假设您确定您的 LinkedHashMap 至少包含两个值，您可以这样做：

Iterator<Map.Entry<String, ReadTableConnectionInfo >> it = tableLists.entrySet().iterator();
if (r.nextFloat() < Read.percentageTable / 100) {
  table = it.next().getValue();
} else { //since you have an else, you have to re-ignore the first value just below
  it.next(); // ignoring the first value
  table = it.next().getValue(); //repeated here in order to get the second value
}

Answer 2

LinkedHashMap 值的迭代按插入顺序排序。所以 values() 是你需要的：

Iterator it = values().iterator();
Object first = it.next().getValue();
Object second = it.next().getValue();