Better Software: introduction to good code

Be#er
So(ware
An
introduc2on
to
good
code

Giordano
Scalzo,
06/05/2009

• Why code matters (10 min)
• Disclaimer
• Good and Bad Code
• The Broken Window Theory
• The Grand Redesign in the Sky
• The Boy Scout Rule
• OOP Patterns and Principles (30 min)
• SOLID Principles
• The Others Principles
• Good code: Smells and heuristics (30 min)
• Comments
• Functions
• General
• Names
• Test
• Conclusion (5 min)
• Q&A? (15 min)

Ward Cunningham
40 years experience
Wiki inventor
Extreme Programming pioneer
Director of Eclipse

Kent Beck

Extreme Programming inventor
JUnit inventor
Tdd inventor

Robert C. Martin

Uncle Bob
40 years experience
Extreme Programming pioneer

while ((!found) && (pos < (fileContent.Length - 6)))
{
byteData = new byte[6];
Array.Copy(fileContent, pos, byteData, 0, 6);
pos = pos + 6;
str_byteData = enc.GetString(byteData);
if (str_byteData.Contains("s"))
{
posE_byteData = str_byteData.IndexOf("s");
pos = pos + (posE_byteData - 6);
pos = pos + 6;
if (byteData[0] == 0x73) // 's'
{
if (byteData[1] == 0x74) // 't'
{
if (byteData[2] == 0x72) // 'r'
{
if (byteData[3] == 0x65) // 'e'
{
if (byteData[4] == 0x61) // 'a'
{
if (byteData[5] == 0x6D) // 'm'
{
found = true;
break;
}
else
{
if (byteData[5] == 0x73)
{
pos = pos - 1;
}
}
}

Netscape

rewrote Netscape 4.0 and released it
after three years as Netscape 6.0

Borland

rewrote dBase and Quattro Pro

Microsoft

rewrote Word

The Boy Scout Rule

Leave the campground cleaner than you found it

S.o.l.i.d. Principles
Solid Principles

Single Responsibility Principle

Only one reason to change

Robustness

Focus

public class PrintServerImpl extends ServiceAdvanced
implements PrintServer, JobListener{
public synchronized String createJob(Object data) { //...
}
public int getStatus(String jobId) { //...
}
public void print(String jobId, int startPage, int endPage) { //...
}
public byte[] getPreview(String jobId, int pageNum) { //...
}
public IRawData getData(String jobId) { //...
}
public void abortAction(String jobId) { //...
}

public Vector getPrinterList() { //...
}
public synchronized void setPrinterList(Vector printerList) { //...
}

public void statusChanged(JobEvent jobEvent) { //...
}
public void pageComputed(JobEvent jobEvent) { //...
}

// ...
}

public class PrinterServerJob {
public synchronized String createJob(Object data) { //...
}
public int getStatus() { //...
}
public void addDataToJob() { //...
}
public void print(){ //...
}
public void print(int startPage, int endPage){ //...
}
public byte[] getPreview(int pageNum){ //...
}
// ...
}

public class PrinterList {
public Vector getPrinterList(){ //...
}
public synchronized void setPrinterList(Vector printerList){ //...
}
}

public class JobEventListener{
public void statusChanged(JobEvent jobEvent){ //...
}
public void pageComputed(JobEvent jobEvent){ //...
}
}

public class PrintServerImpl extends ServiceAdvanced
implements PrintServer, JobListener{
private Map<String, PrinterServerJob> printerServerJob;
private PrinterList printerList;
private JobEventListener jobEventListener;

public PrintServerJob getJob(String jobId) {
return printerServerJob.get(jobId);
}

public Vector getPrinterList(){
return printerList.getPrinterList();
}
public void setPrinterList(Vector printerList){
return printerList.setPrinterList(printerList);
}

public void statusChanged(JobEvent jobEvent){
jobEventListener.statusChanged(jobEvent);
}
public void pageComputed(JobEvent jobEvent){
jobEventListener.pageComputed(jobEvent);
}
//...
}

OpenClose Principle

open for extension

close for modification

abstraction

public static final int TYPE_UNDEFINED = 0;
public static final int TYPE_LEGAL_AG = 1;
public static final int TYPE_LEGAL_PG = 2;
public static final int TYPE_TEMPORARY = 3;
//...
boolean ok = false;
String buildType = m_cdInfo.buildType.toUpperCase();
String prefix = "";
switch (archType) {
case TYPE_LEGAL_AG:
if (buildType.equals("LEGAL_AG")
|| buildType.equals("LEGAL_AGPG")){
ok = true;
}
break;

case TYPE_LEGAL_PG:
if (buildType.equals("LEGAL_PG")
|| buildType.equals("LEGAL_AGPG")){
ok = true;
}
break;

case TYPE_TEMPORARY:
if (buildType.equals("TEMPORARY")
|| buildType.equals("PRV")){
ok = true;
}
prefix = "AP ";
break;
}

if (!ok) {
BurnerHelper.showError(...);
}

public interface ArchiveType {
public boolean isOk(String buildType);
public String getPrefix();
}

public class Undefined implements ArchiveType {
public boolean isOk(String buildType){
return false;
}
public String getPrefix() {
return "";
}
}

public class LegalAg implements ArchiveType {
return buildType.equals("LEGAL_AG") ||
buildType.equals("LEGAL_AGPG")
}
return "";
}
}

public class LegalPg implements ArchiveType {
return buildType.equals("LEGAL_PG") ||
buildType.equals("LEGAL_AGPG")
}
return "";
}
}

public class Temporary implements ArchiveType {
return buildType.equals("TEMPORARY") ||
buildType.equals("PRV")
}
return "AP";
}
}

//...
archTypes.put(0, new Undefined());
archTypes.put(1, new LegalAg());
archTypes.put(2, new LegalPg());
archTypes.put(3, new Temporary());
//...

String buildType = m_cdInfo.buildType.toUpperCase();
boolean ok = archTypes.get(archType).isOk(buildType);
String prefix = archTypes.get(archType).getPrefix();

if (!ok) {
BurnerHelper.showError(...);
}
//...

Liskov Substitution Principle

If for each object o1 of type S there is an object o2 of type T such
that for all programs P defined in terms of T, the behavior of P is
unchanged when o1 is substituted for o2 then S is a subtype of T

Liskov Substitution Principle

Subtypes must be substitutable for their base types

Inheritance and polymorphism

public class Rectangle {
protected int _width;
protected int _height;

public int Width{
get { return _width; }
}

public int Height{
get { return _height; }
}

public virtual void SetWidth(int width){
_width = width;
}

public virtual void SetHeight(int height){
_height = height;
}
}

public class Square: Rectangle {
public override void SetWidth(int width){
_width = width;
_height = width;
}

public override void SetHeight(int height){
_height = height;
_width = height;
}
}

[TestFixture]
public class RectangleTests{
private void CheckAreaOfRectangle(Rectangle r){
r.SetWidth(5);
r.SetHeight(2);
Assert.IsEqual(r.Width * r.Height,10);
}

[Test]
public void PassingTest(){
Rectangle r = new Rectangle();
CheckAreaOfRectangle(r);
}

[Test]
public void FailingTest(){
Rectangle r = new Square();
CheckAreaOfRectangle(r);
}
}

public class Rectangle {
protected int _width;
protected int _height;

public int Width{
get { return _width; }
}

public int Height{
get { return _height; }
}

public virtual void SetWidth(int width){
_width = width;
}

public virtual void SetHeight(int height){
_height = height;
}
}

public class Square {
protected int _side;

public int Side{
get { return _side; }
}

public void SetSide(int side){
_side = side;
}
}

Interface Segregation Principle

Don’t be force to implement unused methods

Avoid “Fat Interfaces”

High cohesion - better understandability, robustness

Low coupling - better maintainability,
high resistance to changes

public interface CartographyListener {
public void poisChanged(Locations pois);
public void cellsChanged(Locations cells);
public void mapChanged(ImageIcon map);
public void updateZoomLevel(int level);
public void updateGeoArea(GeoArea ga);
public void updateGridPosition(Point2D.Double gridPosition);
public void updateMousePosition(Point position);
}

public class CellLayer extends Layer {
/* Methods from CartographyListener interface */
public void cellsChanged(Locations cells) {
setLocations(cells);
}
//.....
}

public class PoiLayer extends Layer {
public void poisChanged(Locations locations) {
setLocations(locations);
}
//.....
}

public abstract class Layer implements CartographyListener, DrawingInterface {
// Metto qui un'implementazione vuota (una sorta di adapter) così
// non sono costretta a sovrascrivere i metodi in tutte le specializzazioni.
public void poisChanged(Locations pois) {}
public void cellsChanged(Locations cells) {}
public void mapChanged(ImageIcon map) {}
public void updateZoomLevel(int level) {
m_zoomLevel = level;
}
public void updateGeoArea(GeoArea ga) {
m_geoArea = ga;
}
public void updateGridPosition(Point2D.Double gridPosition) {}
public void updateMousePosition(Point position) {}
/* End of methods from CartographyListener interface */

//.....
}

public class CartographyUI extends JPanel {
public void addCartographyListener(CartographyListener listener) {
if (m_listeners == null) {
m_listeners = new ArrayList();
}
m_listeners.add(listener);
}

public void setCelles(Locations celles) {
Iterator listeners = m_listeners.iterator();
while (listeners.hasNext()) {
CartographyListener listener =
(CartographyListener)listeners.next();
listener.cellsChanged(celles);
}
updateViewFromLocations();
}

public void setPois(Locations pois) {
CartographyListener listener =
(CartographyListener)listeners.next();
listener.poisChanged(pois);
}
}

//.....
}

public interface CartographyListener {
}

public interface CellListener extends CartographyListener {
public void cellsChanged(Locations cells);
}

public interface PoiListener extends CartographyListener {
public void poisChanged(Locations locations);
}

public class CartographyUI extends JPanel {
public void setCelles(Locations celles) {
CellListener listener =
(CellListener)listeners.next();
listener.cellsChanged(celles);
}
}

public void setPois(Locations pois) {
PoiListener listener =
(PoiListener)listeners.next();
listener.poisChanged(pois);
}
}
public void addCartographyListener(CartographyListener listener) {
Class<?> c = genericObj.getClass();
Class<?> interfaces[] = c.getInterfaces();
for (Class<?> implementedIntf : interfaces) {
if (implementedIntf.getName().equals(
urmetcns.mito.ui.cartography.ui_components.PoiListener"))
poiListeners.add((PoiListener)listener);
if (implementedIntf.getName().equals(
"urmetcns.mito.ui.cartography.ui_components.CellListener"))
cellListeners.add((CellListener)listener);
// ...
}
}

// ...
}

Dependency Injection Principle

Inversion of Control

Hollywood Principle: "don't call us, we will call you"
Dip <> Spring

private boolean retriveCallSideInfo(String Side) {
//...
DeterminationMethod = getXmlOption("Method"); // specify which method to be used

//...
if (DeterminationMethod.equals("PhoneMatch")) {
//...
}

if (DeterminationMethod.equals("Exist")) {
//Query to che the existence of a specified dictionary element
sqlString= "SELECT count(*) AS Cnt FROM iri_dictionary "
" WHERE iri_id = ? and key_dictionary = ?";
pstmt = (OraclePreparedStatement)assocInfo.conn.prepareStatement(sqlString);
pstmt.setLong(1,assocInfo.myIRIId);
pstmt.setString(2,Dictionary);
}

if (DeterminationMethod.equals("Compare")) {
//...
}

if (DeterminationMethod.equals("InOnly")) {
//Query alwais true for the
//provider Telecom Internazionale
sqlString= "SELECT 1 As Cnt FROM Dual";
//...
}

//...

//return true if the info has been found
return (itemFound == 1);

public abstract class CallSideDeterminator {
public abstract boolean findItem();
//...
}

public class CallSideDeterminatorCompare extends CallSideDeterminator {
@Override
public boolean findItem(){
//...
}
}

public class CallSideDeterminatorDFDM extends CallSideDeterminator {
@Override
//...
}
}

public class CallSideDeterminatorPhoneMatch extends
CallSideDeterminator {
@Override
//...
}
}

public class AsExecFindCallSide extends AsCommandExec {
HashMap<String, CallSideDeterminator> strategies=
new HashMap<String, CallSideDeterminator>();

private void init() {
strategies= new HashMap<String, CallSideDeterminator>();

strategies.put("PhoneMatch", new CallSideDeterminatorPhoneMatch());
strategies.put("Compare", new CallSideDeterminatorCompare());
strategies.put("DFDM", new CallSideDeterminatorDFDM());
//...
}

protected boolean retrieveCallSideInfo(String side) {
CallSideDeterminator determinator = null;
if ((determinator = strategies.get(
getXmlOption("Method"))) != null) {
determinator.initDeterminator(assocInfo, side);
if(determinator.findItem()) {
return determinator.storeCIN(side);
}
}
return false;
}
//...
}

Reuse Release Equivalency Principle

The granule of reuse is the granule of release

A package can be considered unit of distribution

A release should have a version number

Black-box, package that is to be used but not changed

Common Closure Principle

Maintainability is more important than reusability

If code must change, all changes should be
in the same package

Common changing classes, should be in the same package

Common Reuse Principle

The classes in a package are reused together
If you reuse one of the classes in a package, you reuse them all

Acyclic Dependencies Principle

Avoid cyclic dependencies
Nightmare to compile
Nightmare to deploy

Least Astonishment Principle

The result of some operation should be obvious, consistent, predictable

Occam’s Razor: The simplest answer is usually the correct answer

int multiply(int a, int b) {
return a + b;
}

int write_to_file(const char* filename, const char* text){
printf("[%s]n", text); /* Note that 'filename' is unused */
}

Law of Demeter

Encapsulation
An object A can request a service (call a method) of
an object instance B, but object A cannot
“reach through” object B to access yet
another object, C, to request its services
An object should avoid invoking methods of
a member object returned by another method
“Don’t talk to stranger"

“Use only one dot"

Inventory.SalesInfo.Items.Count = 2500;

Room.getPlan().canCustomizeWindow()
Room.getPlan().canSelectStyle()
Room.getPlan().hasCeilingFan()

Inventory.SetSalesItemsCount(2500);

Room.canCustomizeWindow()
Room.canSelectStyle()
Room.hasCeilingFan()

Obsolete Comments
Old comments that have lost their meaning

//***********************************************************************************
//! Initalize procedure
/*!
* This methos is called from the main in order to initialize all the thinks<br>
* that the plugin need.
*
* param inLog log that the plugin can use for its own purpose
* return true = all ok false = intialization failed
*/
//***********************************************************************************
public bool init(log4net.ILog inLog)
{
this.log = inLog;
//log.Debug("=======================================================");
log.Debug("============ INIT Module " + getModuleName() + " =========");
return true;
}

public void initLog(log4net.ILog inLog){
log = inLog;
log.Debug("============ INIT Module " + getModuleName() + " =========");
}

Redundant Comments
Version History

/**
*
*
* 03 Oct 2005 - AB - Added the isSameCIDinSameLiuID() function to avoid
different CID in the same LIU (Ticket#2564)
* 09 Sep 2005 - AB - fixed the retriveCallSideInfo() for the PhoneMatch
method (Ticket#2381)
* 06 Sep 2005 - AB - Fixed the SearchProviderDate() to properly work
with the 'DATA' association technique
* 01 Sep 2005 - AB - Added the dupval index exception handling in
saveInHiddenJournal() function
* 27 Jul 2005 - AB - changed the isInformationInDb() to avoid exiting
with assocInfo.lemfList == null
* 27 Jul 2005 - AB - removed the updateJournal() function because not
needed
* 26 Jul 2005 - AB - Now mergeJournal() saves a copy of the two lius ti
be merged in the hidden_journal table
* 26 Jul 2005 - AB - Added the saveInHiddenJournal() function to enhance
the mergeJournal() function
* 05 Jul 2005 - AB - Changed the retriveCallSideInfo queries to select
the correct liu_id in every situation.
…
* 23 Mar 2005 - AB - Added the ORA-00001 error handling in the
AddIRI2Journal
* 9 Mar 2005 - AB - moved the queryExec body function to a generic
queryExec function in the IRITools
* 11 May 2004 - AB - Started
**/

svn ci -m ‘Added the isSameCIDinSameLiuID() (Ticket#2564)’ AssociationFunction.java

Redundant Comments
Repeating the variable name or condition in the comment

//
// list on a file all the Extractors extensions
//
if ( param == "-LISTEXTRACTORS" )
//...

Redundant Comments
Repeating the called method name in a comment after the call

int abs = x.abs(); // Get the absolute value of x
int x = point.getX(); // Get the value of x

int abs = x.abs();
int x = point.getX();

Redundant Comments
Commented Out Code

pos = pos + 9;
//byteData[0] = (byte)fstr.ReadByte();
if (byteData[0] == 0x65) // 'e'
{
//byteData[1] = (byte)fstr.ReadByte();
if (byteData[1] == 0x6E) // 'n'
{
//yteData[2] = (byte)fstr.ReadByte();
if (byteData[2] == 0x64) // 'd'
{
//...
} // 'e'
else
{
//if (byteData[6] == 0x65)
//{
// dataIn.Add(byteData[0]);
// fstr.Seek(-3, SeekOrigin.Current);
//}
//else
{
dataIn.Add(byteData[0]);
//...

pos = pos + 9;
if (byteData[0] == 0x65) // 'e'
{
if (byteData[1] == 0x6E) // 'n'
{
if (byteData[2] == 0x64) // 'd'
{
//...
} // 'e'
else
{
dataIn.Add(byteData[0]);
//...

Redundant Comments
Comments related to structure

//
// Upgrade section
//
if ( param =="-GENERATEUPDATE" || param =="-DOWNLOADUPDATE" || param =="-CHECKUPDATE" )
{
Int32 retVal = ALLOK;
//....
//....
//....
//....
//....
//....
//after 336 more lines of code...
} // End of Upgrade section

protected void build(DynamicView view, File baseTemplate, File outTemplate)
throws ArchiverException, WrEntsException {
//Create required data and column description
List colNames = normalize(view.getDynamicColumnSet());
HashMap lines = new HashMap();
List leftNames = new ArrayList();
List rightNames = new ArrayList();

//Start reading input template and create output copy
BufferedReader r = null;
FileWriter w = null;
if (outTemplate.exists()) {
outTemplate.delete();
}

try {
r = new BufferedReader(new FileReader(baseTemplate));
w = new FileWriter(outTemplate);
String record = null;
boolean sortedBlock = false;
while ((record = r.readLine()) != null) {
if (sortedBlock) {
if (record.toUpperCase().indexOf(
"{END_SORTED_RECS}") >= 0) {
sortedBlock = false;
//Writes required records
String line = null;
//Static first line (if any)...
for (int j = 0; j < leftNames.size(); j++) {
line = (String)lines.get(leftNames.get(j));
if (line != null) {
w.write(line + "n");
}
}

//Sorted lines
for (int j = 0; j < colNames.size(); j++) {
line = (String)lines.get(colNames.get(j));
if (line != null) {
}
}
w.write(record + "n");

//Static last line (if any)...
for (int j = 0; j < rightNames.size(); j++) {
line = (String)lines.get(rightNames.get(j));
if (line != null) {
}
}
}
else {
int index = record.indexOf("{META_REC:");
if (index >= 0) {
String key = record.substring(index + 10,
record.indexOf('}', index));
if (key.indexOf(":") >= 0) {
String values[] = key.split(":");
if (values[1].equals("L")) {
leftNames.add(key);
}
else if (values[1].equals("R")) {
rightNames.add(key);
}
}
lines.put(key, new String(record));
}
}
}

else {
if (record.toUpperCase().indexOf("{START_SORTED_RECS}") >= 0) {
sortedBlock = true;
lines.clear();
leftNames.clear();
rightNames.clear();
}
w.write(record + "n");
}
}
}
catch (Exception e) {
WrCheck.logError("Error build template: " + e.getMessage());
throw new ArchiverException(e);
}
finally {
try {
if (w != null) w.close();
if (r != null) r.close();
} catch (Exception e) {}
}
}

Functions
Deeply nested methods

//From TE-PDF exctractor
if (str_byteData.Contains("s"))
{
posE_byteData = str_byteData.IndexOf("s");
pos = pos + (posE_byteData - 6);
pos = pos + 6;
if (byteData[0] == 0x73) // 's'
{
if (byteData[1] == 0x74) // 't'
{
if (byteData[2] == 0x72) // 'r'
{
if (byteData[3] == 0x65) // 'e'
{
if (byteData[4] == 0x61) // 'a'
{
if (byteData[5] == 0x6D) // 'm'
{
found = true;
break;
}
else
{
{
pos = pos - 1;
}
}
}

else
{
{
pos = pos - 2;
}
else
{
pos = pos - 1;
}
}
}
else
{
{
pos = pos - 3;
}
else
{
pos = pos - 2;
}
}
}
else
{
{
pos = pos - 4;
}
else
{
pos = pos - 3;
}
}
}

else
{
{
pos = pos - 5;
}
else
{
pos = pos - 4;
}
}
}
else
{
pos = pos - 5;
}
}

Functions
Different abstraction level
Composed method
Divide your program into methods that
perform one identifiable task

public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/////si aggancia al file salvato nella mappa dell'oggetto application
String fileId = request.getParameter("FILEID");
if (fileId == null) {
throw new ServletException("Invalid FileId");
}
String partNum = request.getParameter("PART");
int part = 1;
if (partNum != null) {
part = Integer.valueOf(partNum).intValue();
}
boolean isLast = "Y".equals(request.getParameter("LAST"));
boolean getName = "Y".equals(request.getParameter("GETNAME"));
String fileName = MitoDownloadCache.INSTANCE.getFileName(fileId, part);
if (fileName== null) {
throw new ServletException("Invalid FileName");
}

MitoConfig mitoCfg = new MitoConfig();
File file = new File(mitoCfg.getPrintClientDataPath()+"/"+fileName);
if (!file.exists()) {
throw new ServletException("File " + file.getAbsolutePath()
+ " not found");
}

if (getName) {
doDownloadFilename(request, response, file.getName());
} else {
if (isLast) {
MitoDownloadCache.INSTANCE.removeFileList(fileId);
}

doDownload(request, response, file);
file.delete();
}

File file = fileToDownLoad(request);
if (downloadByName(request)) {
} else {
removeFromCacheIfLast(request);
doDownload(request, response, fileToDownLoad(request));
file.delete();
}
}

private boolean downloadByName(HttpServletRequest request) {
return getName;
}

private void removeFromCacheIfLast(HttpServletRequest request)
throws ServletException {
if (isLast) {
MitoDownloadCache.INSTANCE.removeFileList(fileId(request));
}
}

private File fileToDownLoad(HttpServletRequest request)
throws ServletException {
File file;
String fileName = MitoDownloadCache.INSTANCE.getFileName(
fileId(request), part(request));
if (fileName == null) {
}

file = new File(mitoCfg.getPrintClientDataPath() + "/"
+ fileName);
+ " not found");
}
return file;
}

private int part(HttpServletRequest request) {
int part = 1;
}
return part;
}

private String fileId(HttpServletRequest request) throws ServletException {
}
return fileId;
}

Duplication
Dry
“Once, and only once”
Duplication is a missed opportunity for
abstraction

Dead Code
Code that isn’t executed
if statement that checks
for a condition that can’t happen
Private method never called
switch/case conditions that
never occur

Do the right thing: give it a decent burial

Vertical Separation
Variables and function should be defined close
to where they are used

Local variables
should be declared just above their first usage

/////si aggancia al file salvato nella mappa dell'oggetto application
}
int part = 1;
}
String fileName = MitoDownloadCache.INSTANCE.getFileName(fileId, part);
if (fileName== null) {
}

File file = new File(mitoCfg.getPrintClientDataPath()+"/"+fileName);
+ " not found");
}

if (getName) {
} else {
if (isLast) {
MitoDownloadCache.INSTANCE.removeFileList(fileId);
}

doDownload(request, response, file);
file.delete();
}
}

Clutter
Default constructor without implementation
Variables not used
Functions never called
Useless comments

Kill’em all!

Selector Arguments
Avoid boolean arguments
Breaks SRP
Split method in two methods

getLocalPrintService(jobId, data, false);

public static PrintServiceInterface getLocalPrintService(
String jobId, IRawData data,
boolean isStandAlone) throws Exception{
//...
}

public static PrintServiceInterface getEmbeddedLocalPrintService(
String jobId, IRawData data) throws Exception{
//...
}

public static PrintServiceInterface getStandAloneLocalPrintService(
String jobId, IRawData data) throws Exception{
//...
}

Explanatory Vars
Avoid ‘artistic’ programming
Break the calculations up

Matcher match = headerPattern.matcher(line);
if(match.find())
headers.put(match.group(1), match.group(2));

Matcher match = headerPattern.matcher(line);
if(match.find()){
String key = match.group(1);
String value = match.group(2);
headers.put(key.toLowerCase(), value);
}

Magic Numbers
Replace Magic Numbers with Named Constants

m_tx1.setPageHeight(16837);
m_tx1.setPageWidth(11906);

m_tx1.setPageMarginB((int)(0.35 * 1440));
m_tx1.setPageMarginL((int)(0.35 * 1440));
m_tx1.setPageMarginR((int)(0.35 * 1440));
m_tx1.setPageMarginT((int)(0.35 * 1440));
m_tx2.setPageMarginB((int)(0.35 * 1440));
m_tx2.setPageMarginL((int)(0.35 * 1440));
m_tx2.setPageMarginR((int)(0.35 * 1440));
m_tx2.setPageMarginT((int)(0.35 * 1440));

final static double PAGE_HEIGHT = 16837;
final static double PAGE_WIDTH = 11906;
final static int MARGIN = (int)(0.35 * 1440;)

m_tx1.setPageHeight(PAGE_HEIGHT);
m_tx1.setPageWidth(PAGE_WIDTH);

m_tx1.setPageMarginB(MARGIN);
m_tx1.setPageMarginL(MARGIN);
m_tx1.setPageMarginR(MARGIN);
m_tx1.setPageMarginT(MARGIN);
m_tx2.setPageMarginB(MARGIN);
m_tx2.setPageMarginL(MARGIN);
m_tx2.setPageMarginR(MARGIN);
m_tx2.setPageMarginT(MARGIN);

Negative Conditionals
Negatives is harder to understand than positives
Avoid negatives Conditionals

if (!buffer.shouldNotCompact()) {
//...
}

if(!envWarrantsEnabled)
sqlSelect.addWhere(new SqlNot(new SqlEq("LI_TYPE", "ENV")));

if (buffer.shouldCompact()) {
//...
}

if(envWarrantsDisabled)
sqlSelect.addWhere(new SqlNot(new SqlEq("LI_TYPE", "ENV")));

Descriptive Names
Choice descriptive names
Reevaluate the appropriateness of the names

public int x() {
int q = 0;
int z = 0;
for (int kk = 0; kk < 10; kk++) {
if (l[z] == 10) {
q += 10 + (l[z + 1] + l[z + 2]);
z += 1;
}
else if (l[z] + l[z + 1] == 10) {
q += 10 + l[z + 2];
z += 2;
} else {
q += l[z] + l[z + 1];
z += 2;
}
}
return q;
}

public int score() {
int score = 0;
int frame = 0;
for (int frameNumber = 0; frameNumber < 10; frameNumber++) {
if (isStrike(frame)) {
score += 10 + nextTwoBallsForStrike(frame);
frame += 1;
} else if (isSpare(frame)) {
score += 10 + nextBallForSpare(frame);
frame += 2;
} else {
score += twoBallsInFrame(frame);
frame += 2;
}
}
return score;
}

Unambiguous Names
Choose names that make the workings of a
function or variable unambiguous

public boolean stateMachine(int smStatus) {
//...
}

public boolean doAction() {
//...
}

public boolean moveStateMachineToStatus(int smStatus) {
//...
}

public boolean doNextStepInProviderTechnique() {
//...
}

Avoid Encodings
Names should not be encoded with type or
scope information
Hungarian Notation as obsolete legacy

protected int m_FilesCount; // Numero files contenuti nel job
protected int m_VolumesCount; // Numero dischi richiesti dal job (1 sola copia)
protected long m_TotalSize; // Size totale in byte del job
protected int m_VolumesDone; // Numero dischi completati
protected String m_VolDoneList; // Lista dischi completati (durante esecuzione)
protected ArrayList m_labelFields; // Nomi/valori campi da utilizzare in label
private long m_LastModTime; // Data/ora modifica file informativo del job
protected boolean isOnDisk;

protected int filesCount; // Numero files contenuti nel job
protected int volumesCount; // Numero dischi richiesti dal job (1 sola copia)
protected long totalSize; // Size totale in byte del job
protected int volumesDone; // Numero dischi completati
protected String volDoneList; // Lista dischi completati (durante esecuzione)
protected ArrayList labelFields; // Nomi/valori campi da utilizzare in label
private long lastModTime; // Data/ora modifica file informativo del job
protected boolean isOnDisk;

Describe Side Effects
Names should describe everything that a
function, variable, or class is or does

public DiskWriterJobs getJobs() {
if (m_Jobs == null) {
m_Jobs = new DiskWriterJobs(this);
}
return m_Jobs;
}

public DiskWriterJobs createOrReturnJobs() {
if (m_Jobs == null) {
m_Jobs = new DiskWriterJobs(this);
}
return m_Jobs;
}

Insufficient Tests
How many tests? A test suite should test everything that could possibly break

Use a Coverage Tool:
Java
EMMA
Cobertura
Clover
.NET
PartCover
C/C++
BullseyeCoverage
gcov

Beware of Coverage Results

Don’t Skip Trivial Tests
They are better than documentation
Easy today, maybe hard tomorrow

Exhaustively Test Near Bug
Bugs tend to congregate

Tests Should Be Fast
If slow, launched less frequentely
If launched less frequentely, big change between launches and difficult to
know where and when an error was introduced

Readable Code

Test

Avoid Duplication

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