Java Learning Path (i) Java Foundation

Java Naming Conventions

1, the project name all lowercase

2. Package name All lowercase

3. The first letter of the class name is capitalized, if the class name consists of multiple words, the first letter of each word is capitalized.

such as: public class myfirstclass{}

4, the variable name, the method name first letter lowercase, if the name is composed of multiple words, the first letter of each word should be capitalized.

such as: int index=0;

public void ToString () {}

5, the constant name all uppercase

such as: public static final String game_color= "RED";

6. All naming rules must follow the following rules:

1), the name can only be composed of letters, numbers, underscores, $ symbols

2), cannot start with a number

3), name cannot use keywords in java.

4), not to be allowed to appear in Chinese and pinyin naming.

Java Annotation Specification

* @author define creator name

* @param defining incoming parameters; Explaining the meaning of parameters

* @param args (parameters passed in)

* @version The description of the class indicates the version of the module

* @see A reference to the description of classes, properties, methods, or related topics

* @param The description of the method to a parameter in the method

* @return A description of the return result

* @throws exception type. The error code indicates the description of the exception thrown from such a method

/** Attribute Comment */

Variable Comment

Java Output Code

Declaring the scanner class and monitoring the keyboard input stream

Scanner sc = new Scanner (System. in);

System. out. println ("console output statement");

Sc.next ();//Get to keyboard input value

Java Data Type

Data type	Type definition	Type value
Boolean	1 bytes 8 bits	True,false
Byte	1 bytes 8-bit signed integer	-128 ~ + 127
Char	2 bytes 16-bit Unicode characters	Unicode 0 ~ Unicode 216-1
Short	2 bytes 6-bit signed integer	-32768 (-215) ~ + 32767 (+215-1)
Int	4 bytes 32-bit signed integer	-2147483648 (-231) ~ + 2147483647 (231-1)
Long	8 bytes 64-bit signed integer	-263 ~ + 263-1
Float	4-byte 32-bit floating-point number	1.4E-45 ~ 3.4E+38, -1.4E-45 ~ -3.4E+38
Double	8-byte 64-bit floating-point number	4.9E-324 ~ 1.7E+308, -4.9E-324 ~ -1.7E+308

Basic type	Default value
Boolean	Flase
Char	' \u0000 ' (null)
Byte	(byte) 0
Short	(short) 0
Int	0
Long	0L
Float	0.0f
Double	0.0d

logical operators

A	B	！ A	！ B	A&b	A | B	A&&b	A | | B	A^b
True	True	False	False	True	True	True	True	False
True	False	False	True	False	True	False	True	True
False	True	True	False	False	True	False	True	True
False	False	True	True	False	False	False	False	False

Logical NON (! ): Not true or false. It's not fake.

XOR (^): Same as false. The difference is true;

or (|): As long as one is true;

With (&): As long as there is a false is the false;

Three mesh operator: judgment statement? "For true execution", "for false execution";

Calculation operators

Operator	Description
+ 、—、 *,/,%, =, + + 、--	Basic operators
12>>3	Move right 3 times, equivalent to 12/2 of the 3-time Square
3 <<3	Move left 3 times, equivalent to 3*2 3-time
A+=b	A = A+b
A-=b	A = a-b
A*=b	A = A*b
A/=b	A = A/b
A%=b	A = A%b

Java Learning Path (i) Java Foundation