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

Source: Internet
Author: User

—————— 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.)

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