Constructor and instantiation

1. The object is constructed. You cannot create a new object without calling the constructor.
2. Each class, including an abstract class, must have a constructor. Be sure to keep this in mind. However, each class must have a constructor, which does not mean that the programmer must input it.
3. the constructor does not have any return types.

Constructor rules
1. constructors can use any access modifier, including private. (Private constructor means that only the code of this class can instantiate this type of object. Therefore, if the private constructor class wants to allow instances of this class, the class must provide static methods or variables that allow access to instances created from this class );
2. the constructor name must be the same as the class name.
3. the constructor must not have a return type.
4. It is legal (but stupid) to make the method and class have the same name, but this does not make it a constructor. If the returned type is displayed, it is a method rather than a constructor;
5. If you do not enter a constructor in the class code, the compiler automatically generates the default constructor;
6. default constructor always has no parameter constructor.
7. Each constructor must call the overload Constructor (this () or call the parent Constructor (Super () as its first statement.
8. if you do enter a constructor (not dependent on the default constructor generated by the compiler) without calling super (), the compiler inserts a pair of super ().
9. Super () can be called without parameters, or include parameters passed to the parent constructor;
10. You cannot call an instance method or access an instance variable unless the parent constructor is running.
11. You can access static variables and methods, although they can only be used as part of calling super () or this. (Super (animal. dothings ()));
12. abstract classes have constructors, which are always called when a specific subclass is instantiated.
13. The only way to call a constructor is to call it from another constructor.

Public student (INT age, string name)
{
This. Age = age;
This. Name = Name;
}

Constructor:
1. The method and class name are the same
2. No return value
3. used to initialize objects
4. called when the class is instantiated
5. When the class has no constructor, a constructor without parameters is automatically provided.

Execution sequence of the constructor: first parent class and then Child class.