The basic syntax -java

Basic grammar

Java programs can be regarded as a collection of objects, and these objects by calling each other's work methods.

• Object: an instance of a class, we have state and behavior. Specific to a certain thing.
• Class: The class is a template that describes the behavior and state of a class object.
• Methods: that behavior / action, there are many ways a class. Logical operation, data modification, etc.
• Examples of variables: each object has a unique instance variables, the state of the object is determined by the instance variables.

• The basic syntax
• Identifier
• Modifiers
• variable
• Array
• enumerate
• Keyword

Continue Hello World!

    / **
     * This is the Javadoc
     * @author Developer
  * / public class the HelloWorld { public static void main ( String [] args ) { / * * This is a multi-line comment * * / System . OUT . Println ( "the Hello World! " ); // print the character phrase; it is a single line comment } }

The basic syntax

 

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1. Pay attention to grammar

   • Case-sensitive, such as an identifier Hello and hello are not the same
   • Class name, the first letter capitalized, if the stitching together of multiple words, each of the first letter should be capitalized
   • Method names, method names should all start with a lowercase letter, if a plurality of words from the beginning of the second word capitalized ¹
   • Source file name must be the same as the class name. File name suffix.java
   • Method main entrance, all the Java programs public static void main(String[] args){}start

Identifier

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

• All identifiers should be based on capital and lowercase letters, the dollar sign ($) or an underscore (_) begins.
• After the first letter may be the case any combination of letters, dollar signs, underscores, or numbers.
• Keywords can not be used as identifiers

Exercise : Find the following correct and incorrect identifier

-	-	-	-
MyCar	.student	$money	checkPeople
wodeqiche	Student	_youqian	$ _Zhaoren
1mycar	daxueshen_g	youqian + 2	zhao1geren

Modifiers

Java can be modified using the modifier class methods and properties

Access control modifiers: default public protected private
non-access control modifiers: final abstract static sunchronized

variable

1. Local variables
2. Class variables (static variables)
3. Member variables (non-static variables)

Array

Arrays are stored on the heap of objects, you can save multiple variables of the same type.

enumerate

java 5.0 introduces enumeration, limit variables can only be a preset value.

Examples

 class Word{
    enum WordN{NIHAO, HELLO, HI} WordN size; public class WordTest{ public static void main(String[] args) { Word w = new Word(); w.size = word.WordN.HI; } } } 

 

Keyword

Keywords and reserved words can not be used to name

Types of	Keyword	Explanation
Access control	private	private
	protected	be protected
	public	public
Class, method and variable modifiers	abstract	Abstract statement
	class	class
	extends	Expansion inheritance
	final	The final value can not be changed
	implements	Implement (Interface)
	interface	interface
	native	Local, native method (non-Java implementation)
	new	New, created
	static	Static state
	strictfp	Strict, precise
	synchronized	Threads, synchronization
	transient	short
	volatile	Volatile
Program control statements	break	Out of the loop
	case	Selecting a defined value for the switch
	continue	carry on
	default	default
	do	carried out
	else	otherwise
	for	cycle
	if	in case
	instanceof	Examples
	return	return
	switch	Execution based on the value selected
	while	cycle
Error Handling	assert	Whether the assertion expression is true
	catch	Catch an Exception
	finally	There are no exceptions to perform
	throw	Throw an exception object
	throws	Declare an exception might be thrown
	try	Catch the exception
Package Dependencies	import	Introduced
	package	package
basic type	boolean	Boolean
	byte	Byte
	char	Character
	double	Double-precision floating point
	float	Single-precision floating point
	int	Integer
	long	Long integer
	short	Short integer
Variable reference	super	The parent class, the superclass
	this	This class
	void	No return value
Reserved Keywords	goto	Reserved keyword
	const	Reserve
	null	air

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1. Camel nomenclature  ↩