Learning java together [4] --- Original Ecological Data Type

Correction of Java ME: M Refers to Micro, not mobile;
 
Ps: notepad, editplus, ultraedit, and gvim in Windows can be compared with vi, vim, and gedit in Linux;
 
Data Types in java can be divided into two categories:
1) Native Data type; primitive Data type
2) reference type (object type); reference type;
 
How to define variables?
Variable type variable name. [defined in this way]
Example: int;
 
How do I assign values to variables?
Variable name = variable value. [This equal sign is equivalent to a value, rather than an equal sign in the general sense .]
For example, a = 2; 2 is assigned to;
In java, = is used to indicate equal, equivalent to equal signs in mathematics.
 
Variables and constants: the so-called constant is the amount that the value does not change. The so-called variable is the amount that the value can change.
 
Definition and value assignment of Integrated variables:
 
Variable name;
Variable name = variable value;
 
Example: int;
A = 2;
 
You can combine the above two steps into one:
 
Variable type variable name = variable value;
For example, int a = 1;
 
Variable name: in java, the variable name starts with an underscore (_), a letter (_), a $ sign (_), and is followed by a combination of underscores (_), letters (_), $ signs (_), and numbers.
In short, the variable name in java cannot start with a number.
 
There are eight native Data Types in java:
Integer: expressed using int; (32-bit)
Byte type: represented by byte; (-128 ~ + 127 integers between 256 );
Short INTEGER: represented by short; (16 bits)
Long Integer: represented by long; (64-bit)
 
 
Data Representation in computer systems:
Bit: bit (only in the 0, 1 states); is the smallest Data Representation Unit in the computer system.
Bytes: byte, 1 byte = 8bit.
KB: 1KB = 1024 bytes, because the computer's basic code is a binary machine code.
1 MB = 1024KB;
1 GB = 1024 MB;
And so on.
 
Notes in java:
This is a method or means that should be mastered in computer languages. Annotations are for people, not for machines. There are three types of annotations in java;
Single line comment: starts with //, and many content following // will be automatically treated as comment.
Multi-line comment: starts with/* and ends with */. All content in the middle is automatically treated as comment. Multi-line comments are from C/C ++. Note that multi-line comments cannot be nested.
Another multi-line comment: the courage to generate the java DOC help document. I will not introduce it for the moment, because it is not available for the moment.
Author: "Li Yuan Cao"