In java, variables can be defined through the statement "data type identifier;" or "data type identifier = initialization value;"; the identifier is also called the variable name, which consists of numbers (0~9) , uppercase and lowercase letters, underscores, dollar signs ($), RMB signs (￥), and all ASCII codes before hexadecimal 0xc0.
The operating environment of this tutorial: windows7 system, java8 version, DELL G3 computer.
Define/Declare variables
For developers, variables are aliases used to describe a piece of information. One or more variables can be used in program code. Various types of information can be stored in variables, such as login information, version name, file size, a certain English word, and flight ticket price.
In Java, users can declare variables by specifying data types and identifiers. The basic syntax is as follows:
DataType identifier;
or
DataType identifier=value;
The above syntax code involves 3 Each content: DataType, identifier and value, the specific description is as follows:
DataType: variable type, such as int, string, char and double, etc.
identifier: identifier, also called variable name.
value: The value when the variable is declared.
The naming convention for variable identifiers is as follows:
The first character must be a letter, underscore (-), dollar symbol ($) or RMB symbol (￥).
The identifier consists of numbers (0~9), uppercase letters (A~Z), lowercase letters (a~z), underscore (-), dollar sign ($), RMB symbol (￥) and all ASCII codes before hexadecimal 0xc0.
Keywords and reserved words cannot be used as identifiers.
There is no limit on the length of identifiers.
Identifiers are case-sensitive.
The following code declares variables of type String, boolean and int respectively.
String employee; // String 類型的變量 boolean isSave; // boolean 類型的變量 int create_at; // int 類型的變量
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