[Java foundation] basic grammar

Java Code Base Specification

• Case sensitive : Java is case-sensitive, which means that the identifier Hello and hello are different.
• Class Name : For all classes, the class name first letter should be capitalized. If the class name composed of several words, the first letter of each word should be capitalized, such as MyFirstJavaClass.
• Method name : All method name should begin with a lowercase letter. If the method name contains several words, each word is capitalized later.
• Source File name : source file name must be the same as the class name. When saving files, you should use the class name as the file name to save (Remember that Java is case-sensitive), the file name extension is .java. (If the file name and class name are not the same will result in a compilation error).
• Method main entrance : All Java programs started by the public static void main (String args [ ]) method.
• Blank lines, or lines of annotated : Java compiler will be ignored.

 

Java identifier

All components of the Java name is required. Class names, method names and variable names are called tags.

About Java identifiers, the following points should be noted:

• All identifiers should begin with a letter (AZ or az), the dollar sign ($) or an underscore (_)
• After the first character can be any combination of characters
• Keywords can not be used as an identifier
• Identifiers are case sensitive
• Legal identifier, for example: age, $ salary, _value, __ 1_value
• Illegal identifier example: 123abc, -salary

 

Java keywords

Java reserved words are listed below. These reserved words can not be used to name constants, variables, and any identifiers.

Keyword	description
abstract	Abstract method of the abstract class modifiers
assert	Assertion conditions are satisfied
boolean	Boolean data type
break	Label or code segments out of the loop
byte	8-bit signed data type
case	A conditional switch statement
catch	And try to capture with the exception information
char	16-bit Unicode character data type
class	The definition of class
const	Unused
continue	The remaining portion of the loop is not executed
default	Default branch switch statement
do	Loop, the loop body is executed at least once
double	64-bit double precision floating point
else	Branch executed when if condition is not satisfied
enum	Enumerated type
extends	It indicates a class is a subclass of another class
final	Represents a value can not be changed after the initialization of the representation can not be rewritten, or a class can not have subclasses
finally	To complete code execution and design, mainly to the robustness and integrity of the proceedings, whether there are abnormal code execution.
float	32-bit single precision floating point
for	for loop
goto	Unused
if	Conditional statements
implements	Represent a class implements an interface
import	Importing classes
instanceof	Test whether an object is an instance of a class
int	32-bit integer
interface	Define an interface, an abstract type, only of methods and constants
long	64-bit integer
native	It represents a non-implemented method java code
new	Allocating a new instance of the class
package	A series of related classes package
private	Represents private fields, or methods, can only be accessed from within the class
protected	It indicates that the field can only access class or subclass subclasses, or other classes in the same package
public	It represents the total property or method
return	Method returns a value
short	16-bit digital
static	It represents the class level definition, shared by all instances
strictfp	Floating-point comparison using strict rules
super	It represents a base class
switch	Select Statement
synchronized	Code blocks represent the same time can only be accessed by one thread
this	It denotes the current instance of call or call another constructor
throw	Throw an exception
throws	Definition method may throw an exception
transient	Do not modify the sequence of the field
try	It represents a block of code to be done and finally with exception handling or exception is thrown indicating whether the code is executed in the finally
void	Marking method does not return any value
volatile	标记字段可能会被多个线程同时访问，而不做同步
while	while循环

 

Java注释

在Java的编写过程中我们需要对一些程序进行注释。

除了自己方便阅读，更为别人更好理解自己的程序，所以我们需要进行一些注释，可以是编程思路或者是程序的作用，总而言之就是方便自己他人更好的阅读。

Java注释有三种

（1）单行注释：// ...

（2）多行注释：/* ... */

（3）文档注释：/** ... */

例以下小程序，分别展示了三种注释方法。

/**
  * First Program
  * @author Administrator
  *
  */
public class HelloWorld {
    /*
     * 打印字符串 Hello World
     */
    public static void main(String[] args) {
        System.out.println("Hello World"); // 打印 Hello World
    }
}