java - 这种情况下的最佳阵列

Question

在这种情况下，我有一个选择使用哪个数组的问题。有许多数组，如列表、集合等。我想在数组中保留两个这样的数字（这里的数字是随机的）：（多行和 2 列）。

2, 4
4, 8
8, 7
...

但也有这个数组的功能，很容易把第一个数组行放在最后。你能建议我在这种情况下使用什么？

ps 我是新人，所以我想选择最好的选择，这就是我在这里的原因。

Answer 1

您应该更好地创建一个类，例如Pair：

class Pair {
    private int i1;
    private int i2;

    public Pair(int i1, int i2) { this.i1 = i1; this.i2 = i2;  }

    public int getI1() { return i1; }

    public int getI2() { return i2; }
}

然后根据您的特定需要在 、 等ArrayList<Pair>之间进行选择。HashSet<Pair>

Answer 2

Depends on what you mean by saying easily. Easy for programming or high performance. Since you are new, I guess you are looking for the first one. I would stick with an ArrayList<Integer> or an ArrayList<Pair<Integer, Integer>>, where Pair is a custom class like this:

public class Pair<A, B>
{
    public Pair(A a, B b) { this.a = a; this.b = b; }
    public A a;
    public B b;
}

Then use like this:

List<Pair<Integer, Integer>> list = new ArrayList<Pair<Integer, Integer>>();
list.add(new Pair<Integer, Integer>(3, 5));
list.add(new Pair<Integer, Integer>(7, 1));
// now take the first and put it at the end:
list.add(list.remove(0));

---

Edit: If performance of moving the first element to the end is the bottleneck and you want this to go fast, well, then use a LinkedList. This will be an O(1) operation, whereas doing it with an ArrayList, it will be a O(n) operation.

Answer 3

First, you are talking about collections, not arrays: array is one specific kind of collection, and the most primitive one at that. You should use arrays directly when the number of elements in a collection is known at the time the collection is created, and never changes after that.

If your requirement is to remove an element from the beginning of a collection and inserting it at the end, then you should either use a Queue<T> or a LinkedList<T>, and make an object that represents the pair of numbers its generic type argument. These data structures are optimized for quick insertion and removal from the ends.