Use of clone() in Java is tricky and questionable1,2. Effectively, clone() is a copy constructor and for that, the Dart List, Map and Set types each have a named constructor named .from() that perform a shallow copy; e.g. given these declarations Map<String, int> numMoons, moreMoons; numMoons = const <String,int>{ ‘Mars’ : 2, ‘Jupiter’ : 27 … Read more
Why would you want to clone? Creating a new list usually makes more sense. List<String> strs; … List<String> newStrs = new ArrayList<>(strs); Job done.
For deep cloning (clones the entire object hierarchy): commons-lang SerializationUtils – using serialization – if all classes are in your control and you can force implementing Serializable. Java Deep Cloning Library – using reflection – in cases when the classes or the objects you want to clone are out of your control (a 3rd party … Read more
If all you want to do is read the same information more than once, and the input data is small enough to fit into memory, you can copy the data from your InputStream to a ByteArrayOutputStream. Then you can obtain the associated array of bytes and open as many “cloned” ByteArrayInputStreams as you like. ByteArrayOutputStream … Read more
In PHP 5+ objects are passed by reference. In PHP 4 they are passed by value (that’s why it had runtime pass by reference, which became deprecated). You can use the ‘clone’ operator in PHP5 to copy objects: $objectB = clone $objectA; Also, it’s just objects that are passed by reference, not everything as you’ve … Read more
Subclasses may override these methods to provide different semantics. In Object itself, there are two key differences. First, clone copies the singleton class, while dup does not. o = Object.new def o.foo 42 end o.dup.foo # raises NoMethodError o.clone.foo # returns 42 Second, clone preserves the frozen state, while dup does not. class Foo attr_accessor … Read more
As the manual says in Copying Databases you can pipe the dump directly into the mysql client: mysqldump db_name | mysql new_db_name If you’re using MyISAM you could copy the files, but I wouldn’t recommend it. It’s a bit dodgy. Integrated from various good other answers Both mysqldump and mysql commands accept options for setting … Read more
vfork() is an obsolete optimization. Before good memory management, fork() made a full copy of the parent’s memory, so it was pretty expensive. since in many cases a fork() was followed by exec(), which discards the current memory map and creates a new one, it was a needless expense. Nowadays, fork() doesn’t copy the memory; … Read more
(Note: although the cloning version is potentially useful, for a simple shallow copy the constructor I mention in the other post is a better option.) How deep do you want the copy to be, and what version of .NET are you using? I suspect that a LINQ call to ToDictionary, specifying both the key and … Read more
You will need to iterate on the items, and clone them one by one, putting the clones in your result array as you go. public static List<Dog> cloneList(List<Dog> list) { List<Dog> clone = new ArrayList<Dog>(list.size()); for (Dog item : list) clone.add(item.clone()); return clone; } For that to work, obviously, you will have to get your … Read more