比较器基于可配置的顺序 [英] Comparator based on a configurable order

问题描述

有没有办法编写自定义比较器，请按照以下示例：

Is there a way to write custom comparator, following this example:

最多有10个项目以随机顺序进入
ie

There are at most 10 items coming in at a random order i.e.

first item:  item_one
second:      second_one
third:       third_one

我希望将结果排序为： second_one ， third_one ， first_one 。我想从配置文件中提取此顺序，有点像排序模板。

I want result them to be sorted like : second_one, third_one, first_one. I'd like to pull this order from configuration file, sort of like template for sorting.

我使用了错误的数据结构，有没有人有这方面的经验？ / p>

Am I using the wrong data structure, does anyone have experience with this?

推荐答案

当然。这是一个 OrderedComparator ，它根据预定义的顺序比较元素：

Sure. Here is an "OrderedComparator" that compares elements according to a predefined order:

class OrderedComparator implements Comparator<String> {

    List<String> predefinedOrder;

    public OrderedComparator(String[] predefinedOrder) {
        this.predefinedOrder = Arrays.asList(predefinedOrder);
    }

    @Override
    public int compare(String o1, String o2) {
        return predefinedOrder.indexOf(o1) - predefinedOrder.indexOf(o2);
    }

}

这是一些测试代码。 （我使用了 List 而不是 Set ，因为它1）在谈论元素的顺序时似乎更自然2）更好地说明使用此比较器排序时重复元素会发生什么。）

And here is some test code. (I used a List instead of a Set since it 1) seem more natural when talking about the order of the elements and 2) better illustrate what happens with duplicate elements upon sorting using this comparator.)

class Test {

    public static void main(String[] args) {

        // Order (could be read from config file)
        String[] order = { "lorem", "ipsum", "dolor", "sit" };


        List<String> someList = new ArrayList<String>();

        // Insert elements in random order.
        someList.add("sit");
        someList.add("ipsum");
        someList.add("sit");
        someList.add("lorem");
        someList.add("dolor");
        someList.add("lorem");
        someList.add("ipsum");
        someList.add("lorem");


        System.out.println(someList);

        Collections.sort(someList, new OrderedComparator(order));

        System.out.println(someList);
    }

}

输出：

[sit, ipsum, sit, lorem, dolor, lorem, ipsum, lorem]
[lorem, lorem, lorem, ipsum, ipsum, dolor, sit, sit]

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