/**
* Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and values themselves are
* not cloned.
*
* @return a shallow copy of this map
*/
public Object clone() {
HashMap<K, V> result = null;
try {
result = (HashMap<K, V>) super.clone();
} catch (CloneNotSupportedException e) {
// assert false;
}
result.table = new Entry[table.length];
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate(this);
return result;
}
/**
* 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);
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity) capacity <<= 1;
this.loadFactor = loadFactor;
threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
table = new Entry[capacity];
useAltHashing = sun.misc.VM.isBooted() && (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
init();
}
/** Reconstitute the {@code HashMap} instance from a stream (i.e., deserialize it). */
private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException {
// Read in the threshold (ignored), loadfactor, and any hidden stuff
s.defaultReadObject();
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new InvalidObjectException("Illegal load factor: " + loadFactor);
// set hashSeed (can only happen after VM boot)
Holder.UNSAFE.putIntVolatile(
this, Holder.HASHSEED_OFFSET, sun.misc.Hashing.randomHashSeed(this));
// Read in number of buckets and allocate the bucket array;
s.readInt(); // ignored
// Read number of mappings
int mappings = s.readInt();
if (mappings < 0) throw new InvalidObjectException("Illegal mappings count: " + mappings);
int initialCapacity =
(int)
Math.min(
// capacity chosen by number of mappings
// and desired load (if >= 0.25)
mappings * Math.min(1 / loadFactor, 4.0f),
// we have limits...
HashMap.MAXIMUM_CAPACITY);
int capacity = 1;
// find smallest power of two which holds all mappings
while (capacity < initialCapacity) {
capacity <<= 1;
}
table = new Entry[capacity];
threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
useAltHashing = sun.misc.VM.isBooted() && (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
init(); // Give subclass a chance to do its thing.
// Read the keys and values, and put the mappings in the HashMap
for (int i = 0; i < mappings; i++) {
K key = (K) s.readObject();
V value = (V) s.readObject();
putForCreate(key, value);
}
}