实现 Map 并保持插入顺序的 Java 类? [英] Java Class that implements Map and keeps insertion order?

问题描述

我正在寻找具有键值关联但不使用哈希的 Java 类.这是我目前正在做的事情:

I'm looking for a class in java that has key-value association, but without using hashes. Here is what I'm currently doing:

1. 将值添加到 Hashtable.
2. 获取 Hashtable.entrySet() 的迭代器.
3. 遍历所有值并:

1. Add values to a Hashtable.
2. Get an iterator for the Hashtable.entrySet().
3. Iterate through all values and:

1. 为迭代器获取Map.Entry.
2. 根据值创建一个 Module 类型的对象(自定义类).
3. 将类添加到 JPanel.

1. Get a Map.Entry for the iterator.
2. Create an object of type Module (a custom class) based on the value.
3. Add the class to a JPanel.

显示面板.

这样做的问题是我无法控制取回值的顺序，因此我无法按给定顺序显示值(没有对顺序进行硬编码).

The problem with this is that I do not have control over the order that I get the values back, so I cannot display the values in the a given order (without hard-coding the order).

我会为此使用 ArrayList 或 Vector，但稍后在代码中我需要获取给定 Key 的 Module 对象，我不能用 ArrayList 或 Vector.

I would use an ArrayList or Vector for this, but later in the code I need to grab the Module object for a given Key, which I can't do with an ArrayList or Vector.

有谁知道有一个免费/开源的 Java 类可以做到这一点，或者知道一种根据添加时间从 Hashtable 中获取值的方法吗?

Does anyone know of a free/open-source Java class that will do this, or a way to get values out of a Hashtable based on when they were added?

谢谢！

推荐答案

我建议使用 LinkedHashMap 或 TreeMap.LinkedHashMap 保持键的插入顺序，而 TreeMap 通过 Comparator 或自然的 Comparable<保持排序/code> 元素的顺序.

I suggest a LinkedHashMap or a TreeMap. A LinkedHashMap keeps the keys in the order they were inserted, while a TreeMap is kept sorted via a Comparator or the natural Comparable ordering of the elements.

由于不必保持元素排序，LinkedHashMap 在大多数情况下应该更快；TreeMap 对于 containsKey、get、put 具有 O(log n) 性能，和 remove，根据 Javadocs，而 LinkedHashMap 是 O(1) 每个.

Since it doesn't have to keep the elements sorted, LinkedHashMap should be faster for most cases; TreeMap has O(log n) performance for containsKey, get, put, and remove, according to the Javadocs, while LinkedHashMap is O(1) for each.

如果您的 API 只需要可预测的排序顺序，而不是特定的排序顺序，请考虑使用这两个类实现的接口，NavigableMap 或 SortedMap.这将允许您不会将特定实现泄漏到您的 API 中，并在之后随意切换到这些特定类或完全不同的实现.

If your API that only expects a predictable sort order, as opposed to a specific sort order, consider using the interfaces these two classes implement, NavigableMap or SortedMap. This will allow you not to leak specific implementations into your API and switch to either of those specific classes or a completely different implementation at will afterwards.

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