Use java to understand program logic, variables, and java to understand logical variables

Use java to understand program logic, variables, and java to understand logical variables

Data Type	Description	Example
Int	Integer	Used to store integers. For example. Number of trainees. Employee ID of a company. The number of days in a year. Hours per day
Double	Dual-precision floating point	Stores decimal numbers. For example, the price of a product. World price. The amount of loans the World Bank has made to other countries (regions. Employee Salary
Char	Character Type	Stores a single character. For example, male and female. Score: Excellent or poor
String	String type	Stores a string of characters, such as employee name, product model, and product introduction information.

 

 

 

 

 

 

 

 

I. Data Types

1. Data type variable name: (syntax is as follows)

Double score; // declares the storage score of the double Precision Floating Point variable score.

String name; // declare the String variable name to store the Student name

Char sex; // declare the gender of the sex storage variable of the character type.

2. Variable assignment: (syntax)

Variable name = value;

Score = 98.5; // storage 98.5

Name = "James"; // store "James"

Sex = 'male' // store 'male'

3. Combine steps (1). (2) into one

Data type variable name = value; (syntax is as follows)

Double score = 98.5;

String name = "zhangsan ";

Char sex = 'male'

4. Call variables. The stored variables are called call variables.

System. ou. println (variable name );

Ii. variable naming rules

1. The variable must start with a letter. Underline "-" or "$;

2. variables can contain numbers, but cannot start with numbers;

3. Except for the underscore "-". "$", the variable name cannot contain any special characters;

4. Keywords in JAVA cannot be used. Such as int, public, class.

Iii. java provides various operators as follows.

1. Value assignment operator (= );

2. Arithmetic Operators (+,-, *,/, % );

3. Relational operators (>. >=. <. <=. = .! =)

4. Data type conversion is used to facilitate computation between different types of data.

5. Data type conversion includes automatic type conversion and forced type conversion. certain conditions must be met when automatic type conversion occurs.

6. Use the boolean Type in java to indicate true or false. The two values are (true) (false ).

7. In java, Relational operators can be used to compare the size, height, and quantity. The comparison result is of the boolean type.

8. java provides the category class to obtain information entered on the keyboard from the console.