Rising Sun

1、請查看 hashmap 如何初使化

代碼：

 public HashMap(int initialCapacity, float loadFactor) {

        if (initialCapacity < 0)

            throw new IllegalArgumentException("Illegal initial capacity: " +

                                               initialCapacity);

        if (initialCapacity > MAXIMUM_CAPACITY)

            initialCapacity = MAXIMUM_CAPACITY;

        if (loadFactor <= 0 || Float.isNaN(loadFactor))

            throw new IllegalArgumentException("Illegal load factor: " +

                                               loadFactor);

        // Find a power of 2 >= initialCapacity

        int capacity = 1;

        while (capacity < initialCapacity)

            capacity <<= 1;

        this.loadFactor = loadFactor;

        threshold = (int)(capacity * loadFactor);

        table = new Entry[capacity];

        init();

}

當

Map map = new HashMap(9);

while (capacity < initialCapacity)

            capacity <<= 1;

capacity的容量為 16

threshold擴容閥值 16*0.75 =12

和9沒什么關(guān)系 哈

當

Map map = new HashMap(9，1);

capacity的容量為 16

threshold擴容閥值 16*1 =16
不過這個 9 變小一點 就不一樣了 如3時capacity 是4