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Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
The following presents examples for one of the most widely used object-oriented languages, Java, which should cover nearly every way that an object-oriented language can treat this problem. Unlike in C++, objects in Java are always accessed indirectly through references. Objects are never created implicitly but instead are always passed or ...
Python supports most object oriented programming (OOP) techniques. It allows polymorphism, not only within a class hierarchy but also by duck typing. Any object can be used for any type, and it will work so long as it has the proper methods and attributes. And everything in Python is an object, including classes, functions, numbers and modules.
In some of these languages an extra keyword is used to declare no return value; for example void in C, C++ and C#. In some languages, such as Python, the difference is whether the body contains a return statement with a value, and a particular callable may return with or without a value based on control flow.
A basic example is in the argv argument to the main function in C (and C++), which is given in the prototype as char **argv—this is because the variable argv itself is a pointer to an array of strings (an array of arrays), so *argv is a pointer to the 0th string (by convention the name of the program), and **argv is the 0th character of the ...
The object methods include access to the object state (via an implicit or explicit parameter that references the object) whereas class methods do not. If the language supports inheritance , a class can be defined based on another class with all of its state and behavior plus additional state and behavior that further specializes the class.
Downcasting is useful when the type of the value referenced by the Parent variable is known and often is used when passing a value as a parameter. In the below example, the method objectToString takes an Object parameter which is assumed to be of type String.