Dark Horse Programmer--java Foundation--Basic knowledge (I.)

—————— Android Training, Java training, look forward to communicating with you! —————— A java keyword keyword is a word that is predefined in a programming language and gives a special meaning, also known as a reserved word.

Key Words	Description
Abstract	Abstract methods, modifiers for abstract classes
Assert	Whether the assertion condition satisfies
Boolean	Boolean Data types
Break	Jump out of a loop or label code snippet
Byte	8-bit Signed data types
Case	A condition for a switch statement
Catch	Match with try and catch exception information
Char	16-bit Unicode character data type
Class	Defining classes
Const	Not used
Continue	Do not execute the remainder of the loop body
Default	Default branch in the switch statement
Do	Loop statement, the loop body is executed at least once
Double	64-bit double-precision floating-point number
Else	The branch that executes when the IF condition is not established
Enum	Enum type
Extends	Represents a class that is a subclass of another class
Final	Indicates that a value cannot be changed after initialization Indicates that a method cannot be overridden, or that a class cannot have subclasses
Finally	In order to complete the execution of the code design, mainly for the robustness and integrity of the program, regardless of whether there is no exception to execute code.
Float	32-bit single-precision floating-point number
For	For Loop statement
Goto	Not used
If	Conditional statements
Implements	Indicates that a class implements an interface
Import	Import class
instanceof	To test whether an object is an instance of a class
Int	32-bit integer number
Interface	interface, an abstract type, with only the definition of methods and constants
Long	64-bit integer number
Native	Represents methods implemented in non-Java code
New	Assigning a new class instance
Package	A series of related classes make up a package
Private	Represents a private field, or method, etc., accessible only from within the class
Protected	Indicates that a field can only be accessed through a class or its subclasses Subclasses or other classes within the same package
Public	Represents a shared property or method
Return	Method return value
Short	16-digit number
Static	Represents a class-level definition that is shared by all instances of the
Strictfp	Floating-point comparisons use strict rules
Super	Represents a base class
Switch	SELECT statement
Synchronized	A block of code that represents a single thread that can be accessed at the same time
This	Represents the invocation of the current instance or call another constructor
Throw	Throw exception
Throws	Defining exceptions that a method might throw
Transient	Modify fields that do not serialize
Try	Represents a code block to do exception handling or a finally mate to indicate whether throwing an exception executes the code in the finally
void	Tag method does not return any values
Volatile	Tag fields may be accessed by multiple threads at the same time without synchronizing
While	While loop

Two identifier identifiers can be understood as a name, which is used to identify the package name, class name, method name, parameter name, variable name, and so on; there are strict naming conventions for Java identifiers: 1. All identifiers should start with a letter (A-Z or a-Z), a dollar sign ($), or an underscore (_).
2. The first character can be a combination of any character
3. Keywords cannot be used as identifiers
4. Identifiers are case-sensitive

Examples of legal identifiers: Age, $salary, _value, __1_value
Examples of illegal identifiers: 123abc,-salary to make the code more normalized, it is recommended that you follow these naming conventions: 1. All letters are lowercase, for example: Com.java.one. 2. Class name and interface name each word should be capitalized, for example: Arraylist, Iterator. 3. Constant name All letters are capitalized, the words are underlined, for example: Kay_one_honm. 4. The first letter of the variable name and method name is lowercase, beginning with the first letter of each word from the second word, for example: LineNumber. 5. In the program, you should try to use meaningful words to define identifiers to facilitate the program to read, for example: UserName represents the user name. Some of the escaped characters supported in the three Java languages

symbols	character meaning
\ n	Line Break (0x0a)
\ r	Enter (0x0d)
\f	Page Break (0x0c)
\b	BACKSPACE (0x08)
\s	Space (0x20)
\ t	Tabs
\"	Double quotes
\‘	Single quotation marks
\\	Back slash
\ddd	octal character (DDD)
\uxxxx	16 Binary Unicode characters (xxxx)

Dark Horse Programmer--java Foundation--Basic knowledge (I.)