Java-反转ArrayList或对象列表的单一通用方法 [英] Java - a single generic method to reverse ArrayList or List of objects

问题描述

我已经看到有一种非常方便的方法来反转 ArrayList 在这里使用 Collections.reverse（）方法，但是我需要对几种类型的原始对象（例如至少 ArrayList 和 List 的自定义对象。所以 Collections 不能为扩展使用单个方法挽救生命。

I have seen that there is a very convenient way to reverse ArrayList like here using Collections.reverse() method, but I need to achieve such a reverse operation for several types of primitive objects, like at least ArrayList and List of my custom objects. So Collections can't save my life for an extended usage of a single method.

到目前为止，我设法使stg工作（请参见下面的代码），但是我必须写两次：一次用于ArrayList，一次用于List。我将它们命名为相同的名称，因此用法非常方便，但是某些..优化将更加方便：-）。

So far I managed to get stg working (See code below) but I have to write it twice: once for ArrayList and once for List. I named them both the same so usage is very convenient, but some .. optimization would be even more convenient :-).

如何将这两种方法通用化为一个（真实的）通用类？

How to commonalize these 2 methods into a single (real) generic one ?

Thx

/**
 * Generic Reverse Method for ARRAYLIST using Iterator
 * @param ArrayList<Obj_item> notReversed
 * @return ArrayList<Obj_item> reversed
 */
@SuppressWarnings("unchecked")
public static <Obj_item> ArrayList<Obj_item> GenReverseArrayByIterator(ArrayList<Obj_item> mylist) {
                       // ^^^^^^^^^^^^^^^^^^ how to make this generic ?
    // Instanciate
    ArrayList<Obj_item> tmp = new ArrayList<Obj_item>();
    ArrayList<Obj_item> reversed = new ArrayList<Obj_item>();

    // Copy original list
    tmp = mylist;

    // Generate an iterator, starting right after the last element.
    @SuppressWarnings("rawtypes")
    ListIterator myIterator = tmp.listIterator(tmp.size());

    // Iterate in reverse direction
    while (myIterator .hasPrevious()) {
        reversed.add((Obj_item) myIterator.previous());
    }
    return reversed;
}

推荐答案

集合。反向 使用 List<？> 。 ArrayList 实现 List -您可以在 ArrayList 或任何 List 实现。除非我误解了这个问题，否则您的工作似乎完全没有必要。

Collections.reverse takes a List<?>. ArrayList implements List - you can use that method on an ArrayList or any List implementation. What you're doing seems entirely unnecessary, unless I misunderstood the question.

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