jdk1.8 HashMap源码分析（构造函数）

/**
* Constructs an empty <tt>HashMap</tt> with the specified initial
* capacity and load factor.
*
* @param  initialCapacity the initial capacity
* @param  loadFactor      the load factor
* @throws IllegalArgumentException if the initial capacity is negative
*         or the load factor is nonpositive
*/
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);
//默认装载因子0.75
this.loadFactor = loadFactor;
/*
tableSizeFor返回一个数，这个数满足两个条件：
1、大于或等于initialCapacity
2、是2的次幂，如2，4，8，16等

this.threshold：
The next size value at which to resize (capacity * load factor).

// (The javadoc description is true upon serialization.
// Additionally, if the table array has not been allocated, this
// field holds the initial array capacity, or zero signifying
// DEFAULT_INITIAL_CAPACITY.)
int threshold;
*/
this.threshold = tableSizeFor(initialCapacity);
}