JAVA网页编程之Good Java Style: Part 2

但是一些大型开发或者是保密型比较高的项目都会用java，原因有2点，一：java是开源的，不怕别人留后门，偷我工具，.net就不一样了，保持微软的一向风格，源代码不公开GoodJavaStyle:Part2
ByThorntonRose

Introduction
Thisistheconclusionofatwo-partseriesonJavacodingstyle.InGoodJavaStyle:Part1

,IintroducedmycaseforwritingJavacodeusinggoodhabits,explainedwhyweshouldcareaboutthewayourcodelooks,andillustratedsomegeneralelementsofgoodJavastyle.Inthispart,Iillustratemoreelementsofgoodstyleandbringmycasetoaconclusion.

SourceFiles
TherearemanywaysthataJavasourcefilecanbeorganized.Hereisonethatworkswell:


Fileheadercomment(optional).
Packagedeclaration.
Blanklineorotherseparator.
Importstatements.
Blanklineorotherseparator.
Class(es).

Example1.BadFileOrganization.


packageorg.rotpad;
importjava.awt.*;
importjavax.swing.event.*;
importorg.javacogs.*;
importjavax.swing.*;
importjava.awt.event.*;
classFoo{
...
}
publicclassRotPadextendsJFrame{
...
}


Example2.GoodFileOrganization.


packageorg.rotpad;

//Javaclasses
importjava.awt.*;
importjava.awt.event.*;
importjavax.swing.*;
importjavax.swing.event.*;

//JavaCogsclasses
importorg.javacogs.*;

/**
*RotPadisasimpleGUIapplicationforperformingrotationciphersonplain
*text.
*
*@authorThorntonRose
*@version1.0
*/
publicclassRotPadextendsJFrame{
...
}

//-----------------------------------------------------------------------------

/**
*Foois...
*
*@authorThorntonRose
*@version1.0
*/
classFoo{
...
}


ImportStatements
Acomplexclasscanhavealargenumberofimports,whichcangetunruly,especiallyifyouprefertoimportindividualclassesinsteadofwholepackages(e.g.,java.awt.*).Togetahandleonimports,organizethemasfollows:


Javastandardclasses(java.*).
Javaextensionclasses(javax.*).
Third-partyclasses.
Applicationclasses.

Besuretocommentthethird-partyandapplicationclasses,particularlythosethatdonothaveobviousnames.Useend-of-linecomments,orputacommentatthebeginningofthesection.Also,ifyoureallywanttobeaperfectionist,ordereachgroupofimportsalphabetically.

Example3.BadImportStyle.


importjava.util.*;
importjavax.swing.*;
importjava.awt.event*;
importcom.gensym.com.*;
importjavax.swing.table.*;
importcom.pv.jfcx.*;
importjava.awt.*;
importcom.melthorn.util.*;


Example4a.GoodImportStyle.


importjava.awt.*;
importjava.awt.event*;
importjava.util.*;
importjavax.swing.table.*;
importcom.gensym.com.*;//BeanXporter
importcom.pv.jfcx.*;//ProtoView
importcom.melthorn.util.*;//Utilities

Example4b.GoodImportStyle.



//Javaclasses
importjava.awt.*;
importjava.awt.event*;
importjava.util.*;
importjavax.swing.table.*;

//BeanXporter
importcom.gensym.com.*;

//ProtoViewGUIcomponents
importcom.pv.jfcx.*;

//Applicationclasses
importcom.melthorn.util.*;


Classes
OrganizingaJavasourcefilewithoutorganizingtheclassesinitwouldnotgainyoumuchinthewayofproperstyle.Hereshowtoorganizetheclassesinyoursourcefiles:


Javadoccommentorotherheadercomment.
Classdeclaration.
Fielddeclarations.
Blanklineorotherseparator.
Constructors.
Blanklineorotherseparator.
Methods,exceptmain()

,groupedlogically.
Blanklineorotherseparator.
Innerclasses.
Blanklineorotherseparator.
main()

.

Example5.BadClassStyle.


//RotPad--GUIapp.forROTciphering
publicclassRotPadextendsJFrame{
privatestaticfinalStringTRANSFORM_ROT13="ROT13";
privatestaticfinalStringTRANSFORM_ROT13N5="ROT13N5";
privatestaticfinalStringTRANSFORM_ROTASCII="ROT-ASCII";

privatevoidjbInit()throwsException{
...
}

publicstaticfinalStringTITLE="RotPad";
publicstaticfinalStringVERSION="1.0";

publicstaticvoidmain(String[]args){
...
}

publicRotPad(){
...
}

privateJPaneljPanel1=newJPanel();
privateJPaneljPanel2=newJPanel();
privateBorderLayoutborderLayout1=newBorderLayout();
...
}


Example6.GoodClassStyle.


/**
*RotPadisasimpleGUIapplicationforperformingrotationciphersonplain
*text.
*
*@authorThorntonRose
*@version1.0
*/
publicclassRotPadextendsJFrame{
//Publicconstants

publicstaticfinalStringTITLE="RotPad";
publicstaticfinalStringVERSION="1.0";

//Privateconstants

privatestaticfinalStringTRANSFORM_ROT13="ROT13";
privatestaticfinalStringTRANSFORM_ROT13N5="ROT13N5";
privatestaticfinalStringTRANSFORM_ROTASCII="ROT-ASCII";

//GUIcomponents[JBuildergenerated]

privateBorderLayoutborderLayout1=newBorderLayout();
privateJPaneljPanel1=newJPanel();
privateJPaneljPanel2=newJPanel();
...

/**
*Constructanewinstanceofthisclass.
*/
publicRotPad(){
...
}

/**
*InitializeUIcomponents.[JBuildergenerated]
*/
privatevoidjbInit()throwsException{
...
}

...

//--------------------------------------------------------------------------

/**
*Starttheapplication.
*/
publicstaticvoidmain(String[]args){
...
}
}


FieldDeclarations
Someclasseshavealargenumberoffields,whichcanbecomedifficulttomaintainiftheyarenotorganizedwell.Organizethemasfollows:


Publiccontstants(finalandstaticfinal).
Publicvariables.
Protectedconstants.
Protectedvariables.
Packageconstants.
Packagevariables.
Privateconstants.
Privatevariables.

Additionally,usethefollowingguidelinesforwritingfielddeclarations:


Useonedeclarationperline.
UseJavadoccommentsonpublicandprotectedfields,atminimum.
UseUPPERCASEforthenamesofconstants.Usinguppercasemakesthemmuchmoreobviousinbothdeclarationsandexpressions.
Ifyouuseatoolthatgeneratesfielddeclarations,suchasJBuilderorVisualCafe,keepthegeneratedfieldsseparatefromtheotherfields.ItmakesmaintenanceoftheUIcodemucheasier.

Example7.BadFieldStyle.


publicclassCustomerSearchDialogextendsJDialog{
privateJLabelfirstNameLabel=newJLabel();
privateJLabellastNameLabel=newJLabel();
publicstaticfinalRESULT_SELECT=1;
privateVectorresults=newVector();//Searchresults.
privateDefaultTableModeltableModel=newDefaultTableModel();
publicstaticfinalRESULT_CANCEL=0;
//...
}


Example8.GoodFieldStyle.


/**
*...
*/
publicclassCustomerSearchDialogextendsJDialog{
/**
*Indicatesthatsearchwascancelled;returnedbyshowDialog()when
*userclickscancelbutton.
*/
publicstaticfinalRESULT_CANCEL=0;

/**
*Indicatesthatacustomerwasselected;returnedbyshowDialog()when
*userclicksselectbutton.
*/
publicstaticfinalRESULT_SELECT=1;

privateVectorresults=newVector();//Searchresults.
privateDefaultTableModeltableModel=newDefaultTableModel();//Gridmodel.

//GUIfields.[JBuilder]

privateJLabelfirstNameLabel=newJLabel();
privateJLabellastNameLabel=newJLabel();
//...
}


MethodDeclarations
Usethefollowingguidelinesforwritingmethoddeclarations:


AlwayshaveaJavadoccommentorsomeotherheadercomment.
Alwaysputtheaccessmodifierfirst.
Ifthelineistoolong,breakitintooneormorelines.
Ifthemethodhasmorethanafewparameters,considerputtingeachonaseparateline.
Dontputwhitespacebetweenthemethodnameandtheopeningparenthesis("(").
Alwaysputwhitespace(whichcouldbealinebreak)betweentheclosingparenthesis(")")andtheopeningbrace("{").

Example9.BadMethodStyle.


publicintgetTypeCount(StringcustType)
{
...
}
staticpublicgetInstance(){...};
publicvoidshowRange()
throwsRangeException{
...
}


Example10.GoodMethodStyles.


/**
*Returnthesingleinstanceofthisclass.
*/
publicstaticCalculationEnginegetInstance(){
returninstance;
}

/**
*Calculatetheconsumptioncoefficient.
*/
publicfloatcalculateConsumptionCoefficient(intbase,floatvariance,
intiterations)throwsRangeException{
//...
}

/**
*Calculatetheconsumptioncoefficient.
*/
publicfloatcalculateConsumptionCoefficient(
intbase,
floatvariance,
intiterations)
throwsRangeException
{
//...
}

/**
*Calculatetheconsumptioncoefficient.
*/
publicfloatcalculateConsumptionCoefficient(intbase,
floatvariance,
intiterations)
throwsRangeException
{
//...
}


Conclusion
Inconclusion,Ihaveonefinalthoughtforyouonthesubjectofcodestyle.Nomatterwhatguidelinesyoufollow,andnomatterhowferventyourbeliefsaboutthingslikeindentstyle(cf.,Raymond,"IndentStyle"),rememberthatwhenyouwritecodeyouroverallgoalshouldbetomakethecodeunderstandableandmaintainablebysomeoneelse.

RelatedLinks

IndentStyle,TheJargonFile,EricS.Raymond.
Tabsvs.Spaces,JamieZawinski.
WritingRobustJavaCode―TheAmbysoftInc.CodingStandardsforJava,ScottAmbler.
DraftJavaCodingStandard,DougLea.
JavaCodeConventions,SunMicrosystems,Inc.
HowtoWriteDocCommentsforJavadoc,SunMicrosystems,Inc.
TheJargonFile(knowninprintasTheNewHackersDictionary),EricS.Raymond.

AbouttheAuthor
ThorntonRoseisacontractsoftwaredeveloperinAtlanta,Ga.Hecanbereachedviae-mailatthornton.rose@mindspring.com.



java也能做一些底层语言开发做的事情（难度很高，不是java顶尖高手是做不来的），