Java Basics: Variables

#Variables are the basis of all code. In this article, let us learn about the creation and use of variables.

#1. Why use variables?

Variables are used to memorize data. It is a memory system

2. What is variable?

# A variable is a container, an area in memory used to store data.

For example: the memory is a hotel, the variable name is the room name, and the variable value is the person staying in the room

3. Variables three elements? How to declare a variable

Data type: The type of the variable, which determines the size of the variable space

Variable name: The variable name is easy for the computer to find This variable

The value of the variable: the stored data

For example: int number;

Data type	Description
##char(Character type)	Used to store a single character For example: gender 'male', 'female'
int (integer type)	is used to store integers
double(double precision)	is used to store decimals
String(string)	is used to store a string of characters such as "I like programming"

4. How to use variables?

　 (1) Declare a variable int number;

　 (2) Assign number=3;# to the variable

##5. Variable naming rules and specifications?

Rules: The first letter is a letter, underscores '_', and '$' are consistent, and the rest is numbers, letters, underscores, and '$' symbols

Specification: short and clearly indicating the function of the variable. Usually the first letter of the first word is lowercase, and the first letter of subsequent words is capitalized. For example: myName

#6. What should you pay attention to when using variables?

# After a variable is defined, it does not need to be assigned a value, but it cannot be used without assigning a value. It can only be used after it is assigned a value.

Variables have a scope of use.

Variables cannot be redefined, such as: int i; and then another int i; cannot be defined.

.

  public class Test1{ 
      public static void main(String[] args){ 
         int a=0; 
         double b=0.00; 
         char c='酷'; 
         String d="我喜欢java";
         System.out.println(a);
         System.out.println(b);
         System.out.println(c);
         System.out.println(d);
      }
}

Run the above example and the results are as follows:

0
0.00
酷
我喜欢java

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