Switch statement
（重定向自Case statement）
In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via a multiway branch.
Switch statements exist in most high-level imperative programming languages such as Pascal, Ada, C/C++, C# and Java, and in many other types of language, using such keywords as switch, case, select or inspect.