DPCompSci.Java.1718.notebook - …users.desertacademy.org/balei/CompSci/1718/... · •See more at Oracle's BufferedReader page ... HW: Read Kjell, Ch 23 Review & Exercise 5 or 6

DPCompSci.Java.1718.notebook

1

April29,2018

OptionDOOP


2

April29,2018

Conditionals

intx=10if(x


3

April29,2018

Loops

intx=10

while(x12)breakx++

}while(x


4

April29,2018

KeyboardInput

importjava.util.Scannerimportjava.io.* //optionalifyouwanttodeclareSystem.in...

voidechoMe(){

Scannerkeyboard=newScanner(newInputStreamReader(System.in))

System.out.println("Entersometext:")

StringinStr=keyboard.nextLine()

System.out.println("Youanswered:"+inStr+":")

}

KeyboardInputusingScanner

TheScannerclasshandleskeyboardinput

Theclassisinjava.utilsoyouneedtoimportjava.util.Scannertouseit

StartbycreatinganinstanceofaScannerobject.

Scannerobjectshavelotsofmethodstoreadandinterpretinputfromthekeyboard.

YoucanconnecttheScannerclasstovariousinputsourcestheconsole,files,strings,etc.

variable keyboard points to an object of type Scanner

System.in identifies the "standard system input" as the source to be scanned. This is the console.

Scanner objects have a nextLine() method that waits for the user to type something then returns the line entered.

JavaTutorials

SomeofthemoreusefulmethodsoftheScannerclassare:

booleanhasNext(Stringpattern)

Thismethodreturnstrueifthenexttokenmatchesthepatternconstructedfromthespecifiedstring.

booleanhasNextInt()and booleanhasNext()

Thismethodreturnstrueifthenexttokeninthisscanner'sinputcanbeinterpretedasanintvalueinthedefaultradixusingthenextInt()method.

Stringnext(Stringpattern)

Thismethodreturnsthenexttokenifitmatchesthepatternconstructedfromthespecifiedstring.

intnextInt()and next()

Thismethodscansthenexttokenoftheinputasanint.

StringnextLine()

Thismethodadvancesthisscannerpastthecurrentlineandreturnstheinputthatwasskipped.

TheBufferedReaderclassisanotherwaytohandlekeyboardinput

Theclassinheritsfromjava.io.Readerandjava.io.InputStreamReadersoyouneedtoimportthemboth

Usethisclasswhenyoudonotneedtoparsetheinputbutwanttoreadcompletelines.

SeemoreatOracle'sBufferedReaderpage

KeyboardInputusingBufferedReader

https://www.tutorialspoint.com/java/util/java_util_scanner.htmhttps://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html


5

April29,2018

FileInput

importjava.util.Scannerimportjava.io.* //optionalifyouwanttodeclareSystem.in...

voidReadFile(){

try{

System.out.print("Enterthefilenamewithextension:")

Scannerinput=newScanner(newInputStreamReader(System.in))

FileinFile=newFile(input.nextLine())

input=newScanner(inFile)

while(input.hasNextLine()){

Stringline=input.nextLine()

System.out.println(line)

}

input.close()

}catch(Exceptionex){

ex.printStackTrace()

}

}

FileInputusingScanner

TheScannerclassalsohandlesfileinput

ConnectyourScannerobjecttoafilewhenyouinstantiateit.

JavaTutorials

TheBufferedReaderclassisanotherwaytohandlekeyboardinput

Theclassinheritsfromjava.io.Readerandjava.io.InputStreamReadersoyouneedtoimportthemboth

Usethisclasswhenyoudonotneedtoparsetheinputbutwanttoreadcompletelines.

SeemoreatOracle'sBufferedReaderpage

KeyboardInputusingBufferedReader

https://www.tutorialspoint.com/java/util/java_util_scanner.htmhttps://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html


6

April29,2018

3/26/18:Q4Start

OverviewofQ4

JavaDocumentationFileOperations

FileChooserGraphics

CreateaFrameGUIsinNetBeans

ArraysLinkedLists

ConceptsOOPideasAlgorithmsStartonIA

MainAssignmentsMiniProjectIAClient&SolutionIAConceptualPrototype

Someresources: Kjellonlinebook CodingBat ProgrammingbyDoing

http://chortle.ccsu.edu/Java5/index.html#24http://codingbat.com/javahttps://programmingbydoing.com/


7

April29,2018

3/26FileIO

Wherearewe?YoushouldhaveaTestFileScannerclassinyourExercisesprojectsimilartotheonebelow.HowdidIgetthisdocumentation?Let'slook.

Today:StartanewBlueJprojectcalledGUITools.Init,createaclasscalledTestGUIFileIOOurfirstmethodwillbechooseFilewhichusesJava'sJFileChooserclass.

publicFilechooseFile(Stringtitle,StringdefName){JFileChooserfc=newJFileChooser()fc.setDialogTitle(title)fc.setCurrentDirectory(newFile(defName))fc.setSelectedFile(newFile(defName))intresult=fc.showOpenDialog(null)if(result==JFileChooser.APPROVE_OPTION){

System.out.println("Chose"+fc.getSelectedFile()) //debugreturnfc.getSelectedFile()

}System.out.println("Usercancelled") //debugreturnnull

}

JFileChooserisverypowerful.Lookatsomeofitsotherfeaturesto,forexample,showonlydirectories,managethelookandfeel,filtertoonlycertainfiletypes,etc.

Fromnowon,youwillbeexpectedtodocumentyourcode,withaminimumofaheaderforeachclassandmethod.Youmaydothisafterthecodeisdebuggedandworking,butanythingthatyouturninmustbedocumented.

HW:ReadKjell,Ch23Review&Exercise5or6

3/26/18

https://docs.oracle.com/javase/8/docs/api/index.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap23/ch23_1.html


8

April29,2018

3/28FileIOCont

publicFilechooseFile(Stringtitle,StringbuttonText,StringdefName){

JFileChooserfc=newJFileChooser()fc.setDialogTitle(title)fc.setCurrentDirectory(newFile(defName))fc.setSelectedFile(newFile(defName))intresult=fc.showDialog(null,buttonText) //notshowOpenDialogif(result==JFileChooser.APPROVE_OPTION){



}

JFileChooserisverypowerful.Lookatsomeofitsotherfeaturesto,forexample,showonlydirectories,managethelookandfeel,filtertoonlycertainfiletypes,etc.

echoFile():UsechooseFiletocreateamethodthatopensatextfileandechoesthecontentstotheconsole.CallitechoFile().Hint:SeeyourreadFileWErrormethod.

keyboardToFile():UsechooseFiletoopenanoutputfileandenterlinesfromthekeyboardthatgetappendedtothatfile.CallitkeyboardToFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosethefile!

appendToFile():UsechooseFiletoopenaninputfileandanoutputfile.Appendthelinesfromtheinputfiletotheendoftheoutputfile.CallitappendToFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosebothfiles!

loopThroughFile():UsechooseFiletoopenaninputfileandanoutputfile.Loopthroughthelinesfromtheinputfileandwritethemtotheoutputfile,overwritingitifitexists!CallitLoopThroughFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosebothfiles!

NoticethatloopThroughFile()thiscouldbedonedirectlywithJava'sFiles.copy()method.Whywriteourownloop?Wenowhaveatemplateforloopingthroughthelinesofafile,processingtheminsomeway,andthenwritingtheprocessedlinetotheoutputfile.Verypowerful!

HW:ReadKjell,Ch23Review&Exercise5or6

HW:ReadKjell,Ch24

Monday3/26

Wednesday3/28

3/26/18

Toavoidthisinconsistency,IfoundthatwecanuseshowDialoginstead.ItismorecustomizablethanshowOpenDialogandworksthesameonOSXorWindows.Whew!

publicFilechooseFile(Stringtitle,StringdefName){JFileChooserfc=newJFileChooser()fc.setDialogTitle(title)fc.setCurrentDirectory(newFile(defName))fc.setSelectedFile(newFile(defName))intresult=fc.showOpenDialog(null)if(result==JFileChooser.APPROVE_OPTION){



}

Here'sthecodeweusedonMondaytoselectafile:

Wesawthat,onaMac,theshowOpenDialogmethodwasnotallowingustotypeinafilename.

ThesamecodeworksdifferentlyinWindows!

Optiontotypeinfilename

3/28/18

https://docs.oracle.com/javase/8/docs/api/index.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap23/ch23_1.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap24/ch24_1.html


9

April29,2018

4/2Questions

Classes a"SourceCode"file(text.java) a"Compiled"file(binary.class)

> Madeby"compiling"the"sourcecode"into"machinecode"(1's&0's)

a"ClassContext"file(text.ctxt)> A"Buildinstructionfile"

4/2/18

Aswegetintomorecomplicatedterritory,Let'stakeatimeouttogobackandreviewsomeofthebasicconstructsthatwe'veseen:

Projects

Packages

...inJava

...inBlueJ

...inNetBeans(later)

Methodsvs.Functions Basicallythesame Methodsareimplicitly

calledbyanobject,andso,haveaccesstoinformationabouttheparentobject(this).

Javadoesn'treallyhave"functions"sinceallprocessesaredefinedinaClassandhence,calledmethods.

...laterinthesamefile...

...later.stillinthesamefile...

Method(defining)

Methods(calling).

Method(defining)

"Calling"Parameters

ReturnValueNote:TypemustbeFile

ReturnsaValueoftype"File"

Fromanotherpointofview:Variables,runtime,&flowcontrol

...laterinthesamefile...

...later.stillinthesamefile...

At"Runtime" Eventsthatoccurduringthetimethattheprogramisrunning.

FileContentOrganizationimportsmain()(...later...)Classe(s) Classmethods localfunctions

ProgramOrganization Projects Packages Classes Objects Methods Functions Variables

> "primitive"types> Advanced?,Composite?,Civilized?types

Programcreation(building) SourceCode CompiledCode "Build"or"Make"instructionfiles. Run

Programflowcontrol(statements) Syntax Ifthen Ifthenelse whileloops dowhileloops forloops trycatch

Objects ...onlyexistatruntime. ...arespecific"instances"ofaClass ..."carrywiththem"thefieldsandmethodsoftheparentClass ...aregenerallycreatedwitha"constructor"methodoftheClassusingnew.

To"run"appendFile(),forexample CompileTestGUIFileIO(BlueJcreates.classfile)

> Compilers"import"supportingclasses InstantiateanewTestGUIFileIOobject

> Canbedoneinthecodewitha"constructor"method:new

ExecuteamethodfromtheObject> Ifneeded,BlueJwillpromptyouforparameters

VariablesoftypeFile

TryCatchconstruction while

loop

forloop

primitivetypeint

conditionalblockif

"Instantiate"anewobjectfromtheclassJFileChooserusingnew"fcisaJfileChooserobject"

Let'slookatyourKjellExercise23.5or23.6

Whichofthesedoyouhavefinished?

keyboardToFile():UsechooseFiletoopenanoutputfileandenterlinesfromthekeyboardthatgetappendedtothatfile.CallitkeyboardToFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosethefile!

echoFile():UsechooseFiletocreateamethodthatopensatextfileandechoesthecontentstotheconsole.CallitechoFile().Hint:SeeyourreadFileWErrormethod.

PseudocodeforkeyboardToFile

Chooseafile(theoutputfile)CreateaninputScannerobjectfromthekeyboardWritesomegeneralinstructionstotheuserontheconsoleTryto

CreateaPrintwriterconnectedtotheoutputfilePrintaprompt,suchas">",totheconsoleGetthenextlineofinputfromtheconsoleintoastringAslongasthestringisnotofzerolength

PrintthenextlinePrintanotherprompt(">")Getthenextlinefromtheconsole

ClosethePrintWriterwhenfinished(.close()method)CatchanyIOexceptionswithastacktraceClosetheconsole

PrintWriter


10

April29,2018

4/4MoreFileIO

1. 2. 3. Inthecodeshown,

howdoestheuserentertheinputfilename?Inwhatline? [2]

4. Nameatleast2problemswiththistechnique. [2]

5. Nameabettertechnique. [1]

6. Whatline(s)ofcodecouldyouchangetomakeiteasierfortheusertoenteravalidfilename? [2]

7. Describehowyouwoulddothat.Beasspecificasyoucan. [4]

HWQuiz:

1. Generallyspeaking,whatdoesthecodeattherightdo?

2. Fillinthevaluesthatbelonginline:

18: 0 [1]24: sizeA [1]27: sumA=sumA+value

[1]28: count++ [1]32: sumA/sizeA [1]

4/4/18

HW:WriteyesNo()

appendToFile():UsechooseFiletoopenaninputfileandanoutputfile.Appendthelinesfromtheinputfiletotheendoftheoutputfile.CallitappendToFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosebothfiles!

loopThroughFile():UsechooseFiletoopenaninputfileandanoutputfile.Loopthroughthelinesfromtheinputfileandwritethemtotheoutputfile,overwritingitifitexists!CallitLoopThroughFile().Becarefulnottooverwriteafilethatyouwant.Andbesuretoclosebothfiles!

NoticethatloopThroughFile()thiscouldbedonedirectlywithJava'sFiles.copy()method.Whywriteourownloop?Wenowhaveatemplateforloopingthroughthelinesofafile,processingtheminsomeway,andthenwritingtheprocessedlinetotheoutputfile.Verypowerful!


11

April29,2018

4/9Netbeans

Kjell:ReadCh46HW:PBD136:Alittlepuzzle

Hint:OnPBD136youneedtodoalittletricktouseScannertoreadonecharacteratatime.

4/9/18

Download,installNetBeans CreatingagraphicaluserinterfacewithNetBeans

PBD136:Openafilespecifiedbytheuser.Thisfilewillcontainabunchofcharacters.Youshouldreadineachcharacterfromthefile,onecharacteratatime.Displayeverythirdcharacteronthescreen.Throwtheothercharactersaway.Thereisasampleinputfilecalledpuzzle.txt,containingalittlemessageyoucanusetotestyourprogram.Forfun,the"thrownaway"charactersmightsaysomething,too,incaseyoucaretotrytoviewthemsomehow.

CreateaNetBeansProjectsfoldersomewhereonyourcomputerwhereyoucanfindit(likein..\Desert\1718\IBCompSci\NetBeansProjects)StartanewprojectcalledNBExercisesinyourNetBeansProjectsfolder.IdentifytheMainclassasnbexercises.NBExercises.Createamainmethod

Themain()method Alljavaprogramsthatruninastandaloneenvironmentneedamainmethod. Themainmethodcanbeinanyclassthatispartoftheprogram. TheJavavirtualmachinelooksforthemainmethodwhenaprogramisfirstrunto"get

started". Themainmethodcanbeinanyclassthatispartoftheprogram. Atypicalmainmethodmightlooklike:publicstaticvoidmain(String[]args){try{//SetSystemL&FUIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName())program=new

//thecodetorun(test?)goesbelowprogram.method1ToTest()//program.method2ToTest()}catch(Exceptione){e.printStackTrace()}System.exit(0)//necessary

}

This instantiates the class

Task:GetyourloopThroughFilemethodrunninginNetBeans IncludechooseFile(with3parametersandusingaparentdialog) IncludeyourworkingyesNo()method HowdidIgetthedefaultnameofthefiletocopyto?

Next,workonPBD136andfinishitforWed.

PseudocodeforPBD136Choosetheinputfile(puzzle.txtorpuzzle2.txt)Tryto

ConnecttheinputfiletoaScannerobject(sowecanreadit)Aslongasthereisanotherlineintheinputfile

GetthenextlineConnectthelinetoaScannersowecanloopthroughcharactersSetthedelimiterto""sowecangetonecharacteratatimeAslongasthelinehasanothercharacter

ifthepositionisamultipleof3printthecharactertotheconsole

Closetheinputfilewhenfinished(.close()method)CatchanyIOexceptionswithastacktrace

Kjell:ReadCh46HW:PBD136:Alittlepuzzle

All further programming work should be done in NetBeans

https://programmingbydoing.com/a/a-little-puzzle.htmlhttps://stackoverflow.com/questions/2597841/scanner-method-to-get-a-charhttps://www.youtube.com/watch?v=JZTIIchUa6Ehttps://programmingbydoing.com/a/a-little-puzzle.html


12

April29,2018

4/11Arrays

int[]myIntArray //declareanarrayofintegersmyIntArray=newint[10] //createitwith10elements

char[]myCharArray=newchar[10] //a10elementarrayofchars

//youcaninitializetovaluesString[]myStringArray={"Pine","Fred","Avacado","granite"}

for(ints:){System.out.println("valueofx:"+x)

}

Arrays

Anorderedgroupofelements

ArraysareobjectsfromanArraysclass,withassociatedmethods

Elementscanbeprimitivetypesorobjects

Needtobedeclaredandcreated(canbedoneinonestatement)

Needtoknowthesizewhenit'screated

JavaTutorials

DotheseriesofexercisesPBD138141,BasicArrays.Pleasefollowtheinstructionsexactly.Emailmethe.javafilethatcontainsyourcode.ThemethodnamesshouldbePBD138,PBD139,PBD140,andPBD141

4/11/18

PBD138:Createanarraythatcanholdtenintegers.Fillupeachslotofthearraywiththenumber113.Thendisplaythecontentsofthearrayonthescreen,eachvalueonaseparaterow. Donotusealoop.Also,donotuseanyvariablefortheindexyoumustuseliteral

numberstorefertoeachslot.

PBD139:Createanarraythatcanholdtenintegers.Fillupeachslotofthearraywiththenumber113.Thendisplaythecontentsofthearrayonthescreen,eachvalueonaseparaterow. Thistime,youmustusealoop,toputthevaluesinthearrayandalsotodisplaythem.

Also,intheconditionofyourloop,youshouldnotcountuptoaliteralnumber.Insteadyoushouldusethelengthfieldofyourarray.

PBD140:Createanarraythatcanholdtenintegers.Fillupeachslotofthearraywitharandomnumberfrom1to100.Thendisplaythecontentsofthearrayonthescreen. Youmustusealooptofillthearray. And,likelasttime,youmustusethelengthfieldofyourarrayandnotaliteral

number(like10)intheconditionoftheloop.

PBD141:Createanarraythatcanhold1000integers.Fillthearraywithrandomnumbersintherange1099.Thendisplaythecontentsofthearrayonthescreeninrowsof20. Youmustusealooptofillthearray. Ifyou'recarefultoonlypickrandomnumbersfrom10to99andyouputtwospaces

aftereachnumber,thenyouroutputwilllineupasbelow. Andifyoudon'tknowhowtopickrandomnumbersinacertainrange,seethe

HW:PBD138141BasicArrays

HW:PBD138141BasicArrays

nextInt()methodoftheRandomclassinJavadocs.

https://www.tutorialspoint.com/java/java_arrays.htmhttps://programmingbydoing.com/a/basic-arrays-0.htmlhttps://programmingbydoing.com/a/basic-arrays-1.htmlhttps://programmingbydoing.com/a/basic-arrays-2.htmlhttps://programmingbydoing.com/a/basic-arrays-3.htmlhttps://programmingbydoing.com/a/basic-arrays-0.htmlhttps://programmingbydoing.com/a/basic-arrays-0.htmlhttps://docs.oracle.com/javase/8/docs/api/java/util/Random.html#nextInt-int-


13

April29,2018

4/13Arrayalgorithms

JavaTutorials

4/13/18

Inclasstoday,youwillworkonKjell:Ch47

HW:KjellCh47Ex46Onceyouhavereadit,workonExercises46FinishforMonday

JavaTutorials

4/16/184/20/18

Inclasstoday,andWedwewillworkonKjell:Ch49C(2DArrays)

HW:KjellCh49CExercises1,2,4,5,6&7(optional)

Onceyouhavereadit,workonExercises1,2,4,5,6&7(optional)FinishforMonday4/23

4/23/184/27/18 Morewitharraysandsorting

https://www.tutorialspoint.com/java/java_arrays.htmhttp://chortle.ccsu.edu/Java5/Notes/chap47/ch47_1.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap47/progExercises47.htmlhttps://www.tutorialspoint.com/java/java_arrays.htmhttp://chortle.ccsu.edu/Java5/Notes/chap47/ch47_1.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap49C/progExercises49C.html


14

April29,2018

4/27Arrayalgorithms

4/27/18

37 12 20 16 8 44 19

SortingAlgorithms

ExchangesortForeachelementinthearray,startingwiththefirstone:

CompareeachoftheremainingelementstothefirstoneIfanyelementislargerthanthefirstone,swapthetwo.

i3


15

April29,2018

5/2GraphicsIntro

4/30/18

PBD160:Bubblesort PBD161:Selectionsort

5/2/18

KjellCh36:GraphicsHW:KjellCh36Exercises16

5/4/18

KjellCh37:MoregraphicsideasHW:KjellCh37MiniProject(DueWed,5/9)

http://www.algolist.net/Algorithms/Sorting/Bubble_sorthttp://www.algolist.net/Algorithms/Sorting/Selection_sorthttp://chortle.ccsu.edu/Java5/Notes/chap36new/ch36_1.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap36new/progExercises36.htmlhttp://chortle.ccsu.edu/Java5/Notes/chap36new/ch36_1.html

Attachments

JavaCheatSheet.pdf

DPCS.MiniProject.pdf

THE JAVA LANGUAGE CHEAT SHEET

Primitive Types: INTEGER: byte(8bit),short(16bit),int(32bit),

long(64bit),DECIM:float(32bit),double(64bit)

,OTHER: boolean(1bit), char (Unicode)

HEX:0x1AF,BINARY:0b00101,LONG:8888888888888L

CHAR EXAMPLES: a,\n,\t,\,\\,\

Primitive Operators Assignment Operator: = (ex: int a=5,b=3; )

Binary Operators (two arguments): + - * / %

Unary Operators: + - ++ --

Boolean Not Operator (Unary): !

Boolean Binary: == != > >= < >>>

Ternary Operator: bool?valtrue:valfalse;

Casting, Conversion int x = (int)5.5; //works for numeric types

int x = Integer.parseInt(123);

float y = Float.parseFloat(1.5);

int x = Integer.parseInt(7A,16); //fromHex

String hex = Integer.toString(99,16);//toHex

//Previous lines work w/ binary, other bases

java.util.Scanner, input, output Scanner sc = new Scanner(System.in);

int i = sc.nextInt(); //stops at whitespace

String line = sc.nextLine(); //whole line

System.out.println(bla); //stdout

System.err.print(bla); //stderr,no newline

java.lang.Number types Integer x = 5; double y = x.doubleValue();

double y = (double)x.intValue();

//Many other methods for Long, Double, etc

java.lang.String Methods //Operator +, e.g. fat+cat -> fatcat

boolean equals(String other);

int length();

char charAt(int i);

String substring(int i, int j); //j not incl

boolean contains(String sub);

boolean startsWith(String pre);

boolean endsWith(String post);

int indexOf(String p); //-1 if not found

int indexOf(String p, int i); //start at i

int compareTo(String t);

//a.compareTo(b) -> -1

String replaceAll(String str, String find);

String[] split(String delim);

StringBuffer, StringBuilder StringBuffer is synchronized StringBuilder

(Use StringBuilder unless multithreaded)

Use the .apend( xyz ) methods to concat

toString() converts back to String

java.lang.Math Math.abs(NUM),Math.ceil(NUM),Math.floor(NUM)

,Math.log(NUM),Math.max(A,B),Math.min(C,D),

Math.pow(A,B),Math.round(A),Math.random()

IF STATEMENTS: if( boolean_value ) { STATEMENTS }

else if( bool ) { STATEMENTS }

else if( ..etc ) { STATEMENTS }

else { STATEMENTS }

//curly brackets optional if one line

LOOPS: while( bool ) { STATEMENTS }

for(INIT;BOOL;UPDATE) { STATEMENTS }

//1INIT 2BOOL 3STATEMENTS 4UPDATE 5->Step2

do{ STATEMENTS }while( bool );

//do loops run at least once before checking

break; //ends enclosing loop (exit loop)

continue; //jumps to bottom of loop

ARRAYS: int[] x = new int[10]; //ten zeros

int[][] x = new int[5][5]; //5 by 5 matrix

int[] x = {1,2,3,4};

x.length; //int expression length of array

int[][] x = {{1,2},{3,4,5}}; //ragged array

String[] y = new String[10]; //10 nulls

//Note that object types are null by default

//loop through array:

for(int i=0;i

POLYMORPHISM: Single Inheritance with extends

class A{ }

class B extends A{ }

abstract class C { }

class D extends C { }

class E extends D

Abstract methods

abstract class F {

abstract int bla();

}

class G extends F {

int bla() { //required method

return 5;

}

}

Multiple Inheritance of interfaces with

implements (fields not inherited)

interface H {

void methodA();

boolean methodB(int arg);

}

interface I extends H{

void methodC();

}

interface K {}

class J extends F implements I, K {

int bla() { return 5; } //required from F

void methodA(){} //required from H

boolean methodB(int a) { //req from A

return 1;

}

void methodC(){} //required from I

}

Type inference:

A x = new B(); //OK

B y = new A(); //Not OK

C z = new C(); //Cannot instantiate abstract

//Method calls care about right hand type

(the instantiated object)

//Compiler checks depend on left hand type

GENERICS: class MyClass {

T value;

T getValue() { return value; }

}

class ExampleTwo {

A x;

B y;

}

class ExampleThree {

A list;

B head;

}

//Note the extends keyword here applies as

well to interfaces, so A can be an interface

that extends List

JAVA COLLECTIONS: List: Similar to arrays

ArrayList: Slow insert into middle

//ArrayList has fast random access

LinkedList: slow random access

//LinkedList fast as queue/stack

Stack: Removes and adds from end

List Usage:

boolean add(T e);

void clear(); //empties

boolean contains(Object o);

T get(int index);

T remove(int index);

boolean remove(Object o);

//remove uses comparator

T set(int index, E val);

Int size();

List Traversal:

for(int i=0i

DP Computer Science: Mini-Project Alei 2017-18

C:\Users\Bob\Documents\Dropbox\Desert\DP CompSci\DPCompSciNotes.docx on 4/28/18 at 9:11 PM Page 1 of 1

Create your own picture Description: Create a program that draws a picture illustrating some of what we have recently learned about arrays and graphics. This is an individual project. You may not work together. If you have questions or need help debugging, you may ask me or anyone else who is not in the course. Requirements: Your program should create a JPanel within a JFrame window that:

Includes at least one each of line, oval (or circle), rectangle, and polygon

Uses a background color other than the default

Uses at least three different colors of fill

Uses at least one custom color that is not a predefined Java constant

Has some elements other than lines that scale with the size of the window

Contains at least one repeated element with properties controlled by one or more arrays

Exits when the red x box is pressed. Deliverables:

The .java file containing your main class and any other classes that you create.

A screen shot of the picture(s) that your code produces

A hand drawn, scale diagram on a grid indicating the shapes that make up your drawing along with their initial sizes and positions.

Assessment Rubric:

A. Creativity

0-1 Shows little or no creativity

2-3 Shows some creativity

4-5 Shows a lot of creativity

B. Complexity

0-1 Does not meet the minimum requirements

2-3 Meets the minimum requirements

4-5 Above and beyond the minimum requirements

C. Coding Style

0-1 Poor formatting Minimal or no documentation Inefficient or incorrect use of code repetition, hard coded values, etc. Poor choice of variable names

2-3 Some incorrect formatting Missing documentation Reasonably efficient and mostly correct use of code Mostly appropriate choices for variable names

4-5 Good use of formatting to make the code readable Complete but concise documentation, including inline comments as appropriate Very efficient and correct use of code minimal repetition, creative use of methods Thoughtful choices for all variable names

Hint: Start with a simple design that meets the requirements. Write clean code. Then add creativity and complexity.

SMART Notebook

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