On 30/01/2012 13:16, Ulf Zibis wrote:
Isn't cloning faster than normal instantiation?
I can imagine, that behind the scenes cloning mainly only needs to
duplicate the binary footprint of an object.
I don't see a good reason why it should be (equally, I've not tried
benchmarking).
For the immediate fields of an object, (partial) bitwise copying "by
hand" should be of comparable performance to a bitwise clone. For
copying the referenced objects, there is no benefit for the clone.
Implementation of HashMap.clone is:
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;
The "copy constructor" is slightly different in that it uses the default
load factor (and minimum size) instead of copying.
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
putAllForCreate(m);
Tom
