1. What is an object? An object is an instance of a class, a new object is created, and a different attribute is given to the object to materialize it. A class can have more than one object, an object can call a number of different methods, the equivalent of a dog-given calls, wagging the tail and so on. 2. Object-oriented and process-oriented differences:* The process emphasizes behavior, which is to analyze the steps needed to solve the problem, and then use the function to implement these steps one step at a time. * Object-oriented is based on process-oriented, constituting the problem transaction into individual objects, the object is not to complete a step, but to describe something in the whole problem-solving steps of the behavior.
| |
process-oriented |
object-oriented |
| design ideas |
top down, hierarchical, decomposition |
bottom-up, object, synthetic |
| Program Unit |
Function module |
Object |
| Design method |
program = algorithm + data structure |
program = object = data + method |
| advantages |
Independent, code-sharing |
approach to the way people think simulation of the objective world |
| Disadvantages |
inconsistent data and programs Maintenance Difficulties |
the disordered nature of the objective world The concept is immature |
3. There are three main characteristics of object-oriented:* Inheritance is the technique of building a new class using the definition of an existing class, inheriting the method number or variable of the parent class, calling (inheriting: the subclass name +extends+ the parent class name) under the modifiers allowed, and invoking the parent class's method with the object of the subclass. Method overrides the method in the parent class after the output call is overridden by the method of the subclass, the variable cannot be overridden (overwritten), and the concept of "overriding" is only for methods. rewrite: Shift+alt+s selects the return Super.foots () that appears in the program of the Override/implenment methods class, meaning that the method of executing the parent class will output two values without deleting the words. Overrides are variable and method names unchanged, others can be changed.
* Encapsulation: wrapping something together and presenting it in a new and complete form;
the process of hiding properties, methods, or implementation details is called encapsulation;
encapsulation is a matter of selectively exposing or hiding certain information, which solves the problem of data security.
* Polymorphism: The rewriting of methods, overloading and dynamic connections constitute polymorphism. Polymorphism is also divided into design-time polymorphism and run-time polymorphism. Overloading is run-time polymorphic, and overrides are compile-time polymorphism.
Java Course: 2.java Object-oriented
