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In VBA, an assignment of variables of type Object is a shallow copy, an assignment for all other types (numeric types, String, user defined types, arrays) is a deep copy. So the keyword Set for an assignment signals a shallow copy and the (optional) keyword Let signals a deep copy. There is no built-in method for deep copies of Objects in VBA.
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 ...
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 ...
The rule of three (also known as the law of the big three or the big three) is a rule of thumb in C++ (prior to C++11) that claims that if a class defines any of the following then it should probably explicitly define all three: [1] destructor; copy constructor; copy assignment operator; These three functions are special member functions. If ...
Array's destructor deletes the data array of the original, therefore, when it deleted copy's data, because they share the same pointer, it also deleted first's data. Line (2) now accesses invalid data and writes to it. This produces a segmentation fault. If we write our own copy constructor that performs a deep copy then this problem goes away.
In C++, by contrast, objects are copied automatically whenever a function takes an object argument by value or returns an object by value. Additionally, due to the lack of garbage collection in C++, programs will frequently copy an object whenever the ownership and lifetime of a single shared object would be unclear.
Define a Prototype object that returns a copy of itself. Create new objects by copying a Prototype object. This enables configuration of a class with different Prototype objects, which are copied to create new objects, and even more, Prototype objects can be added and removed at run-time. See also the UML class and sequence diagram below.
Java and C++ are two prominent object-oriented programming languages.By many language popularity metrics, the two languages have dominated object-oriented and high-performance software development for much of the 21st century, and are often directly compared and contrasted.