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Many languages allow generic copying by one or either strategy, defining either one copy operation or separate shallow copy and deep copy operations. [1] Note that even shallower is to use a reference to the existing object A, in which case there is no new object, only a new reference. The terminology of shallow copy and deep copy dates to ...
In Java, the Object class contains the clone() method, which copies the object and returns a reference to that copied object. Since it is in the Object class, all classes defined in Java will have a clone method available to the programmer (although to function correctly it needs to be overridden at each level it is used). Cloning an object in ...
For example, strings and arrays are passed by reference, but when modified, they are duplicated if they have non-zero reference counts. This allows them to act as value types without the performance problems of copying on assignment or making them immutable. [8] In the Qt framework, many types are copy-on-write ("implicitly shared" in Qt's terms).
Prototype object: a specialized metaobject that creates new objects by copying itself; Singleton object: only instance of its class for the lifetime of the program; Filter object: receives a stream of data as its input and transforms it into the object's output; A common anti-pattern is the God object, an object that knows or does too much.
Copy constructors define the actions performed by the compiler when copying class objects. A Copy constructor has one formal parameter that is the type of the class (the parameter may be a reference to an object). It is used to create a copy of an existing object of the same class.
For example, given a binary tree of infinite depth, a depth-first search will go down one side (by convention the left side) of the tree, never visiting the rest, and indeed an in-order or post-order traversal will never visit any nodes, as it has not reached a leaf (and in fact never will). By contrast, a breadth-first (level-order) traversal ...
The default implementation of Object.clone() performs a shallow copy. When a class desires a deep copy or some other custom behavior, they must implement that in their own clone() method after they obtain the copy from the superclass. The syntax for calling clone in Java is (assuming obj is a variable of a class type that has a public clone ...
(For arrays containing nil values, you can use compressSparseArray first.) The function tries to preserve the order of the array: the earliest non-unique value is kept, and all subsequent duplicate values are removed. For example, for the table {5, 4, 4, 3, 4, 2, 2, 1} removeDuplicates will return {5, 4, 3, 2, 1}.