Static method
1.static can be used to modify method.
2. A method modified by static is called static method.
3. Syntax: access modifier static returns value type method name (parameter list) {//method implementation}
4. Note: there is no order between access modifier and static.
5. Use class name, static method name (argument) (recommended) object name, static method name (argument).
6 . Precautions for static methods:
(1) Only static methods or static properties of this class can be directly accessed in static methods;
(2) Non-static members (properties and methods) of this class cannot be directly accessed in static methods.
(3) Static attributes and static methods of this class can be directly accessed in non-static methods.
(4) this/super keyword cannot be used in static methods;
(5) Static methods are allowed to be inherited, and static methods with the same name as the parent class can be defined in subclasses.