Java Basic syntax

1. Keywords

access Control : Private (privately) protected public (common)

class , method and variable modifiers : Abstract class extends final implements interface native new static STRICTFP synchronized Transient Vol Atile

Program Control: Break continue return does while if-else for instanceof switch case default

error handling : Try cathc throw throws

packet-related : Import package base type: Boolean byte char double float int long short null true false

variable reference : Super this void

reserved words : Goto const

2. identifiers

2.1 definition

1:java a sequence of characters, called identifiers, is used when naming features such as variables, methods, and classes.

2: As long as it is possible to name the place is called the identifier.

2.2 legal definition of identifiers

1: Written by 26 English letters, number 0-9, symbol: _ or $ composition.

2: Numbers can not begin.

4:java are strictly case-sensitive and have unlimited lengths.

5: Identifiers do not contain spaces.

2.3 Java Name Naming conventions

1: Package Name: All letters are lowercase when multiple words are composed. such as: xxxyyyzzz

2: Constant Name: All letters are capitalized, and multiple words are joined with underscores. Xxx_yyy_zzz

3: Class name Interface name: Multi-word composition is all the first letter capitalized. Hump writing: XXXYYYZZZ 4: Variable name and function name: When multiple words are composed, the first letter is lowercase, and then the first letter of the word is capitalized. Xxxyyyzzz

3. Notes

1, single-line (single-line) Comment: "//..."

2. Block comment: "/*......*/"

3. Document Comment: "/**......*/"

4. Javadoc annotation Tag syntax

@author description of the class indicates the author of the development of such a module

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

@see a reference to the description of classes, properties, methods, and related topics

Description of a parameter in a method @param description of the method

Description of the method return value @return The description of the method

@exception the description of the method, describe the exceptions that the method might throw

4. Constants

? Constant indicates a value that cannot be changed

? Categories of Constants in Java:

1. Integer constants. All integers

2. Decimal constants. All decimals

3. Boolean constants. More unique, only two values. True False

4. Character constants. Identifies a numeric letter or symbol with a single quotation mark (' ')

5. String constants. Identify one or more characters in double quotation marks

6. NULL constant. There is only one value: null

? For integers: Java has four forms of representation

1. Binary

2. Decimal

3. Eight binary: 0-7, full 8 into 1, denoted by the beginning of 0.

4.16 binary: 0-9,a-f, full 16 in 1, beginning with 0x.

5. Negative number binary representation

Small rule: The highest number of negative numbers is 1, the original numbers are reversed and added 1

Java Basic syntax