10WriteafilterTenPerLine.javathattakesasequenceofintegersbetween0and99andprints10integersperline,withcolumnsaligned.ThenwriteaprogramRandomIntSeqthattakestwocommand-lineargumentsMandNandoutputsNrandomintegersbetween0andM-1.TestyourprogramswiththecommandjavaRandomIntSeq200100|javaTenPerLine.
11WriteaprogramWordCount.javathatreadsintextfromstandardinputandprintsoutthenumberofwordsinthetext.Forthepurposeofthisexercise,awordisasequenceofnon-whitespacecharactersthatissurroundedbywhitespace.
12Writeaprogramthatreadsinlinesfromstandardinputwitheachlinecontaininganameandtwointegersandthenusesprintf（）toprintatablewithacolumnofthenames,theintegers,andtheresultofdividingthefirstbythesecond,accuratetothreedecimalplaces.Youcoulduseaprogramlikethistotabulatebattingaveragesforbaseballplayersorgradesforstudents.
13Whichofthefollowingrequiresavingallthevaluesfromstandardinput（inanarray,say）,andwhichcouldbeimplementedasafilterusingonlyafixednumberofvariables?
Foreach,theinputcomesfromstandardinputandconsistsofNrealnumbersbetween0and1.
∙Printthemaximumandminimumnumbers.
∙Printthekthsmallestvalue.
∙Printthesumofthesquaresofthenumbers.
∙PrinttheaverageoftheNnumbers.
∙Printthepercentageofnumbersgreaterthantheaverage.
∙PrinttheNnumbersinincreasingorder.
∙PrinttheNnumbersinrandomorder.
14Writeaprogramthatprintsatableofthemonthlypayments,remainingprincipal,andinterestpaidforaloan,takingthreenumbersascommand-linearguments:
thenumberofyears,theprincipal,andtheinterestrate（seeExercise1.2.24）.
15WriteaprogramClosest.javathattakesthreecommand-lineargumentsx,y,z,readsfromstandardinputasequenceofpointcoordinates（xi,yi,zi）,andprintsthecoordinatesofthepointclosestto（x,y,z）.Recallthatthesquareofthedistancebetween（x,y,z）and（xi,yi,zi）is（x-xi）2+（y-yi）2+（z-zi）2.Forefficiency,donotuseMath.sqrt（）orMath.pow（）.
16Giventhepositionsandmassesofasequenceofobjects,writeaprogrmtocomputetheircenter-of-massorcentroid.ThecentroidistheaveragepositionoftheNobjects,weightedbymsass.Ifthepositionsandmassesaregivenby（xi,yi,mi）,thenthecentroid（x,y,m）isgivenby:
m=m1+m2+...+mN
x=（m1x1+...+mnxN）/m
y=（m1y1+...+mnyN）/m
WriteaprogramCentroid.javathatreadsinasequenceofpositionsandmasses（xi,yi,mi）fromstandardinputandprintsouttheircenterofmass（x,y,m）.Hint:
modelyourprogramafterAverage.java.
17WriteaprogramSignalAnalyzer.javathatreadsinasequenceofrealnumbersbetween-1and1andprintsouttheiraveragemagnitude,averagepower,andthenumberofzerocrossings.Theaveragemagnitudeistheaverageoftheabsolutevaluesofthedatavalues.Theaveragepoweristheaverageofthesquaresofthedatavalues.Thenumberofzerocrossingsisthenumberoftimesadatavaluetransitionsfromastrictlynegativenumbertoastrictlypositivenumber,orviceversa.Thesethreestatisticsarewidelyusedtoanalyzedigitalsignals.
18WriteaprogramCheckerBoard.javathattakesacommand-lineargumentNandplotsanN-by-Ncheckerboardwithredandblacksquares.Colorthelowerleftsquarered.
19Writeaprogramthattakesascommand-lineargumentsanintegerNandadoublevaluep（between0and1）,plotsNequallyspacedpointsofsizeonthecircumferenceofacircle,andthen,withprobabilitypforeachpairofpoints,drawsagraylineconnectingthem.
20Writecodetodrawhearts,spades,clubs,anddiamonds.Todrawaheart,drawadiamond,thenattachtwosemicirclestotheupperleftandupperrightsides.
21WriteaprogramRose.javathattakesacommand-lineargumentNandplotsarosewithNpetals（ifNisodd）or2Npetals（ifNiseven）byplottingthepolarcoordinates（r,θ）ofthefunctionr=sin（N×θ）forθrangingfrom0to2πradians.BelowisthedesiredoutputforN=4,7,and8.
22WriteaprogramBanner.javathattakesastringsfromthecommandlineanddisplayitinbannerstyleonthescreen,movingfromlefttorightandwrappingbacktothebeginningofthestringastheendisreached.Addasecondcommand-lineargumenttocontrolthespeed.
23ModifyPlayThatTune.javatotakeadditionalcommand-lineargumentsthatcontrolthevolume（multiplyeachsamplevaluebythevolume）andthetempo（multiplyeachnotesdurationbythetempo）.
24Writeaprogramthattakesthenameofa.wavfileandaplaybackraterascommand-lineargumentsandplaysthefileatthegivenrate.First,useStdAudio.read（）toreadthefileintoanarraya[].Ifr=1,justplaya[];otherwisecreateanewarrayb[]ofapproximatesizertimesa.length.Ifr<1,populateb[]bysamplingfromtheoriginal;ifr>1,populateb[]byinterpolatingfromtheoriginal.Thenplayb[].
25WriteprogramsthatusesStdDrawtocreateeachofthefollowingdesigns.
26
27WriteaprogramCircles.javathatdrawsfilledcirclesofrandomsizeatrandompositionsintheunitsquare,producingimageslikethosebelow.Yourprogramshouldtakefourcommand-linearguments:
thenumberofcircles,theprobabilitythateachcircleisblack,theminimumradius,andthemaximumradius.
CreativeExercises
28Visualizingaudio.ModifyPlayThatTune.javatosendthevaluesplayedtostandarddrawing,sothatyoucanwatchthesoundwavesastheyareplayed.Youwillhavetoexperimentwithplottingmultiplecurvesinthedrawingcanvastosynchronizethesoundandthepicture.
29Statisticalpolling.Whencollectingstatisticaldataforcertainpoliticalpolls,itisveryimportanttoobtainanunbiasedsampleofregisteredvoters.AssumethatyouhaveafilewithNregisteredvoters,oneperline.WriteafilterthatprintsoutarandomsampleofsizeM（seeProgram1.4.1）.
30Terrainanalysis.Supposethataterrainisrepresentedbyatwo-dimensionalgridofelevationvalues（inmeters）.Apeakisagridpointwhosefourneighboringcells（left,right,up,anddown）havestrictlylowerelevationvalues.WriteaprogramPeaks.javathatreadsaterrainfromstandardinputandthencomputesandprintsthenumberofpeaksintheterrain.
31Histogram.Supposethatthestandardinputstreamisasequenceofdoublevalues.WriteaprogramthattakesanintegerNandtwodoublevalueslandrfromthecommandlineandusesStdDrawtoplotahistogramofthecountofthenumbersinthestandardinputstreamthatfallineachoftheNintervalsdefinedbydividing（l,r）intoNequal-sizedintervals.
32Spirographs.WriteaprogramSpirograph.javathattakesthreecommand-lineargumentsR,r,andaanddrawstheresultingspirograph.Aspirograph（technically,anepicycloid）isacurveformedbyrollingacircleofradiusraroundalargerfixedcircleorradiusR.Ifthepenoffsetfromthecenteroftherollingcircleis（r+a）,thentheequationoftheresultingcurveattimetisgivenby
x（t）=（R+r）*cos（t）-（r+a）*cos（（（R+r）/r）*t）
y（t）=（R+r）*sin（t）-（r+a）*sin（（（R+r）/r）*t）
Suchcurveswerepopularizedbyabest-sellingtoythatcontainsdiscswithgearteethontheedgesandsmallholesthatyoucouldputapenintotracespirographs.
Foradramatic3deffect,drawacircularimage,e.g.,earth.gifinsteadofadot,andshowitrotatingovertime.Here'sapictureoftheresultingspirographwhenR=180,r=40,anda=15.
33Clock.WriteaprogramClock.javathatdisplaysananimation
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