[C#]ArrayList初始容量

2012-05-15

很多書都寫 ArrayList 的初始容量是16個元素，

但測試出來，看起來並不是這樣，~~超過 8 個元素，才開始為16的倍數。(有點傻，太執意在16了)~~

Allen老師講解，預設為4 ，之後*2

private static void Main(string[] args)
        {
            ArrayList none = new ArrayList();
            Console.WriteLine(none.Capacity);

            ArrayList one = new ArrayList();
            one.Add(1);
            one.Add(2);
            Console.WriteLine(one.Capacity);

            ArrayList two = new ArrayList();
            two.Add(1);
            two.Add(2);
            two.Add(3);
            two.Add(4);
            two.Add(5);
            Console.WriteLine(two.Capacity);

            ArrayList three = new ArrayList();
            three.Add(1);
            three.Add(2);
            three.Add(3);
            three.Add(4);
            three.Add(5);
            three.Add(6);
            three.Add(7);
            three.Add(8);
            three.Add(9);
            three.Add(10);
            three.Add(11);
            three.Add(12);
            three.Add(13);
            three.Add(14);
            three.Add(15);
            three.Add(16);
            three.Add(17);
            three.Add(18);
            three.Add(19);
            three.Add(20);
            Console.WriteLine(three.Capacity);

            int capacity = 8;
            ArrayList tmp = new ArrayList(capacity);
            Console.WriteLine(tmp.Capacity);

            tmp.TrimToSize();
            Console.WriteLine(tmp.Capacity);
        }

OutPut ：

順便紀錄一下 ArrayList 可自訂初始容量，和調整到目前實際擁有元素的大小，加入元素的數量大於自訂，ArrayList 會自動調整容量。

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