The methods of the class include
1, method name
2, return value type
3, method body
Member variables: properties of the class; can be called by other classes or methods
local variable: a variable within a method; can only be used within its method
OOP: Object Oriented Programming
Method with parameters: The type, quantity and order of the formal parameters need to be in one-to-one correspondence. The parameter can be a number or multiple numbers, arrays or objects.