Objektorienteret programmering i Java

320 Pages·2007·3.063 MB·Danish

by  Jacob Nordfalk

Jacob Nordfalk
J
Objektorienteret programmering i
ava
4. udgave
FG811-3 - kolofon - OOPJava4.indd 1 21-11-2007 13:11:37
Objektorienteret
programmering i
Java
Copyright:
2007© by Forlaget Globe A/S
4. udgave, 2. oplag
Udgiver:
Forlaget Globe A/S
Skodsborgvej 305
2850 Nærum
Tlf. 70 15 14 00
Fax [phone]
E-mail: [email protected]
Internet: http://www.globe.dk
Forfatter:
Jacob Nordfalk
Forlagsredaktion:
Carsten Straaberg
([email protected])
Omslag:
Carsten Straaberg
DtP:
Jacob Nordfalk
Sats:
Forlaget Globe A/S, Nærum
Tryk:
Eurographic Danmark, Taastrup
Printed in Denmark 2009
ISBN: 978-87-7900-811-3
Forlaget Globe og forfatteren kan ikke holdes
økonomisk ansvarlig for eventuelle fejl og
mangler i bogen.
www.globe.dk
Bøg om fritid, hobby, IT og erhverv
FG811-3 - kolofon - OOPJava4.indd 2 21-11-2007 13:11:37
Indholdsfortegnelse
0 Forord......................................................................................15
0.1 Bogens opbygning.......................................................................................15
0.1.1 Veje gennem bogen..............................................................................................................15
0.1.2 Kapitlernes opbygning..........................................................................................................17
0.2 Til underviseren............................................................................................17
0.3 Ændringer i fjerde udgave...........................................................................18
0.4 Tak.................................................................................................................18
1 Introduktion.............................................................................19
1.1 Programmering.............................................................................................20
1.1.1 Styresystemet.......................................................................................................................20
1.1.2 Hvorfor lære at programmere? ............................................................................................20
1.1.3 Et simpelt program................................................................................................................20
1.1.4 Hvordan lærer man at programmere....................................................................................21
1.2 Fordele og ulemper ved Java......................................................................21
1.2.1 Stærke sider.........................................................................................................................21
1.2.2 Stor opbakning......................................................................................................................22
1.2.3 Svagheder............................................................................................................................22
1.3 Programmeringsværktøjer til Java.............................................................23
1.3.1 Borland JBuilder...................................................................................................................23
1.3.2 Eclipse.org............................................................................................................................24
1.3.3 Oracle JDeveloper................................................................................................................25
1.3.4 NetBeans..............................................................................................................................26
1.3.5 BlueJ.....................................................................................................................................27
1.3.6 Andre værktøjer....................................................................................................................27
1.3.7 Sun JDK................................................................................................................................27
1.4 Hjælp og videre læsning..............................................................................28
1.4.1 Projekter med åben kildekode..............................................................................................28
2 Basal programmering............................................................29
2.1 Det første javaprogram................................................................................30
2.1.1 Kommentarer........................................................................................................................30
2.1.2 Klassedefinitionen.................................................................................................................31
2.1.3 Oversættelse og kørsel af programmet................................................................................31
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2.2 Variabler........................................................................................................33
2.2.1 Heltal.....................................................................................................................................33
2.2.2 Sammensætte strenge med +..............................................................................................34
2.2.3 Beregningsudtryk..................................................................................................................34
2.2.4 Kommatal..............................................................................................................................35
2.2.5 Matematiske funktioner.........................................................................................................37
2.2.6 Kald af metoder....................................................................................................................38
2.2.7 Logiske variabler...................................................................................................................38
2.2.8 Opgaver................................................................................................................................39
2.3 Betinget udførelse........................................................................................39
2.3.1 Indlæsning fra tastaturet.......................................................................................................40
2.3.2 if-else....................................................................................................................................41
2.3.3 Opgaver................................................................................................................................41
2.4 Blokke............................................................................................................42
2.4.1 Indrykning.............................................................................................................................42
2.5 Løkker............................................................................................................43
2.5.1 while-løkken..........................................................................................................................43
2.5.2 for-løkken..............................................................................................................................45
2.5.3 Indlejrede løkker...................................................................................................................46
2.5.4 Uendelige løkker...................................................................................................................47
2.5.5 Opgaver................................................................................................................................47
2.6 Værditypekonvertering................................................................................48
2.6.1 Eksplicit typekonvertering.....................................................................................................48
2.6.2 Implicit typekonvertering.......................................................................................................49
2.6.3 Misforståelser omkring typekonvertering..............................................................................49
2.7 Fejl.................................................................................................................50
2.7.1 Indholdsmæssige (logiske) fejl.............................................................................................50
2.7.2 Sproglige fejl.........................................................................................................................50
2.7.3 Køretidsfejl............................................................................................................................51
2.8 Test dig selv..................................................................................................52
2.9 Resumé..........................................................................................................53
2.9.1 Gode råd om programmering...............................................................................................53
2.10 Opgaver.......................................................................................................54
2.10.1 Befordringsfradrag..............................................................................................................54
2.10.2 Kurveprogram.....................................................................................................................54
2.11 Appendiks...................................................................................................55
2.11.1 Navngivningsregler.............................................................................................................55
2.11.2 De simple typer...................................................................................................................55
2.11.3 Værditypekonvertering........................................................................................................55
2.11.4 Aritmetiske operatorer........................................................................................................56
2.11.5 Regning med logiske udtryk...............................................................................................57
2.11.6 Sammenligningsoperatorer.................................................................................................57
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2.12 Avanceret....................................................................................................58
2.12.1 Grafiske indtastningsvinduer..............................................................................................58
2.12.2 Formatere tal og datoer......................................................................................................59
2.12.3 Primtal.................................................................................................................................60
2.12.4 Klassemetoder....................................................................................................................60
2.12.5 Kombination af logiske operatorer......................................................................................62
2.12.6 Alternativudtryk...................................................................................................................63
2.12.7 Brug af ++ og -- (optælling og nedtælling)..........................................................................63
2.12.8 Brug af += og -=..................................................................................................................63
2.12.9 do-while-løkken...................................................................................................................63
2.12.10 break.................................................................................................................................64
2.12.11 continue............................................................................................................................64
2.12.12 break og continue med navngivne løkker.........................................................................64
2.12.13 switch................................................................................................................................65
2.12.14 Komma i for-løkker...........................................................................................................65
3 Objekter...................................................................................67
3.1 Objekter og klasser......................................................................................68
3.2 Punkter (klassen Point)................................................................................69
3.2.1 Erklæring og oprettelse.........................................................................................................69
3.2.2 Objektvariabler......................................................................................................................70
3.2.3 Metodekald...........................................................................................................................70
3.2.4 Eksempel..............................................................................................................................71
3.2.5 Import af standardklasser.....................................................................................................72
3.3 Rektangler (klassen Rectangle)..................................................................72
3.3.1 Konstruktører........................................................................................................................72
3.3.2 Metoder.................................................................................................................................73
3.3.3 Metoders returtype................................................................................................................74
3.3.4 Metoders parametre.............................................................................................................75
3.4 Tekststrenge (klassen String).....................................................................76
3.4.1 Streng-objekter er uforanderlige...........................................................................................77
3.4.2 Man behøver ikke bruge new til String-objekter...................................................................78
3.4.3 Navnesammenfald for metoder............................................................................................78
3.4.4 At sætte strenge sammen med +..........................................................................................78
3.4.5 Sammenligning.....................................................................................................................79
3.4.6 Opgaver................................................................................................................................80
3.5 Lister (klassen ArrayList)............................................................................80
3.5.1 Gennemløb af lister..............................................................................................................82
3.5.2 Eksempel: Eventyrfortælling.................................................................................................82
3.5.3 Eksempel: Punkter i en liste.................................................................................................82
3.5.4 Historisk bemærkning: Lister før JDK 1.5.............................................................................83
3.5.5 Eksempel: Blanding af kort med ArrayList............................................................................84
3.6 Datoer (klassen Date)...................................................................................85
3.6.1 Opgaver................................................................................................................................86
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3.7 Test dig selv..................................................................................................87
3.8 Resumé..........................................................................................................87
3.9 Appendiks.....................................................................................................88
3.9.1 Klassen Point........................................................................................................................88
3.9.2 Klassen Rectangle................................................................................................................89
3.9.3 Klassen String.......................................................................................................................90
3.9.4 Specialtegn i strenge............................................................................................................91
3.9.5 Klassen Date........................................................................................................................92
3.9.6 Klassen ArrayList..................................................................................................................93
3.10 Avanceret....................................................................................................94
3.10.1 Sætte strenge sammen (klassen StringBuilder).................................................................94
3.10.2 Standardmetoder til at arbejde med lister...........................................................................96
3.10.3 Lister af simple typer (autoboxing)......................................................................................96
3.10.4 Andre slags lister og mængder...........................................................................................96
3.10.5 Nøgleindekserede tabeller (klassen HashMap)..................................................................97
4 Definition af klasser...............................................................99
4.1 En Boks-klasse...........................................................................................100
4.1.1 Variabler.............................................................................................................................100
4.1.2 Brug af klassen...................................................................................................................101
4.1.3 Metodedefinition.................................................................................................................101
4.1.4 Flere objekter......................................................................................................................102
4.2 Indkapsling..................................................................................................103
4.3 Konstruktører..............................................................................................105
4.3.1 Standardkonstruktører........................................................................................................106
4.3.2 Opgaver..............................................................................................................................106
4.4 En Terning-klasse.......................................................................................107
4.4.1 Opgaver..............................................................................................................................108
4.5 Relationer mellem objekter........................................................................108
4.5.1 En Raflebæger-klasse........................................................................................................108
4.5.2 Opgaver..............................................................................................................................110
4.6 Nøgleordet this...........................................................................................111
4.7 Ekstra eksempler........................................................................................112
4.7.1 En n-sidet terning................................................................................................................112
4.7.2 Personer.............................................................................................................................114
4.7.3 Design af klasser................................................................................................................115
4.8 Test dig selv................................................................................................116
4.9 Resumé........................................................................................................116
4.9.1 Formen af en klasse...........................................................................................................117
4.9.2 Formen af en metode.........................................................................................................118
6 - OBJEKTORIENTERET PROGRAMMERING I JAVA
4.10 Opgaver.....................................................................................................119
4.10.1 BlueJ.................................................................................................................................119
4.10.2 Fejlfinding.........................................................................................................................120
4.11 Avanceret..................................................................................................122
4.11.1 Bankkonti..........................................................................................................................122
4.11.2 Opgaver............................................................................................................................122
5 Nedarvning............................................................................123
5.1 At udbygge eksisterende klasser.............................................................124
5.1.1 Eksempel: En falsk terning.................................................................................................124
5.1.2 At udbygge med flere metoder og variabler........................................................................126
5.1.3 Nøgleordet super................................................................................................................126
5.1.4 Opgaver..............................................................................................................................127
5.2 Polymorfe variabler....................................................................................128
5.2.1 Dispensation fra traditionel typesikkerhed..........................................................................128
5.2.2 Polymorfi.............................................................................................................................129
5.2.3 Eksempel på polymorfi: Brug af Raflebaeger.....................................................................129
5.2.4 Hvilken vej er en variabel polymorf ?..................................................................................130
5.2.5 Reference-typekonvertering...............................................................................................131
5.3 Eksempel: Et matador-spil........................................................................132
5.3.1 Polymorfi.............................................................................................................................138
5.3.2 Opgaver..............................................................................................................................138
5.4 Stamklassen Object...................................................................................139
5.4.1 Referencer til objekter.........................................................................................................140
5.5 Konstruktører i underklasser....................................................................141
5.5.1 Konsekvenser.....................................................................................................................142
5.6 Ekstra eksempler........................................................................................143
5.6.1 Matadorspillet version 2......................................................................................................143
5.6.2 Opgaver..............................................................................................................................145
5.7 Test dig selv................................................................................................146
5.8 Resumé........................................................................................................146
5.9 Avanceret....................................................................................................147
5.9.1 Initialisering uden for konstruktørerne................................................................................147
5.9.2 Kald af en konstruktør fra en anden konstruktør................................................................148
5.9.3 Metoder erklæret final.........................................................................................................148
5.9.4 Metoder erklæret protected................................................................................................148
5.9.5 Variabel-overskygning........................................................................................................148
6 Pakker....................................................................................149
6.1 At importere klassedefinitioner.................................................................150
6.2 Standardpakkerne......................................................................................150
6.2.1 Pakken java.lang................................................................................................................151
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6.3 Pakkers placering på filsystemet..............................................................151
6.4 At definere egne pakker.............................................................................152
6.4.1 Eksempel............................................................................................................................152
6.5 Pakke klasser i jar-filer (Java-arkiver)......................................................152
6.5.1 Eksekverbare jar-filer..........................................................................................................153
6.6 Test dig selv................................................................................................153
6.7 Resumé........................................................................................................153
6.8 Opgaver.......................................................................................................153
6.9 Avanceret: public, protected og private...................................................154
6.9.1 Variabler og metoder..........................................................................................................154
6.9.2 Indkapsling med pakker......................................................................................................154
6.9.3 Klasser................................................................................................................................154
7 Lokale, objekt- og klassevariabler......................................155
7.1 Klassevariabler og -metoder.....................................................................156
7.1.1 Eksempler på klassevariabler.............................................................................................157
7.1.2 Eksempler på klassemetoder.............................................................................................157
7.2 Lokale variabler og parametre..................................................................158
7.2.1 Parametervariabler.............................................................................................................158
7.3 Test dig selv................................................................................................160
7.4 Resumé........................................................................................................160
7.4.1 Tilknytning...........................................................................................................................160
7.4.2 Adgang til variabler og metoder..........................................................................................160
7.4.3 Adgang fra metoder............................................................................................................160
7.5 Avanceret....................................................................................................161
7.5.1 Introduktion til rekursive algoritmer.....................................................................................161
7.5.2 Rekursion: Beregning af formel..........................................................................................162
7.5.3 Rekursion: Listning af filer..................................................................................................163
7.5.4 Rekursion: Tegning af fraktaler...........................................................................................164
8 Arrays....................................................................................165
8.1 Erklæring og brug......................................................................................166
8.1.1 Eksempel: Statistik.............................................................................................................167
8.1.2 Initialisere et array med startværdier..................................................................................167
8.1.3 Arrayet i main()-metoden....................................................................................................168
8.2 Gennemløb og manipulering af array.......................................................168
8.3 Array af objekter.........................................................................................169
8.3.1 Polymorfi.............................................................................................................................169
8.4 Arrays versus lister (ArrayList).................................................................169
8.5 Resumé........................................................................................................170
8.6 Opgaver.......................................................................................................170
8 - OBJEKTORIENTERET PROGRAMMERING I JAVA
8.7 Avanceret....................................................................................................171
8.7.1 Flerdimensionale arrays.....................................................................................................171
8.7.2 Konvertere mellem arrays og lister.....................................................................................172
9 Grafiske programmer...........................................................173
9.1 Klassen Graphics.......................................................................................175
9.1.1 Eksempel: Grafikdemo.......................................................................................................176
9.1.2 Eksempel: Kurvetegning.....................................................................................................177
9.2 Metoder du kan kalde.................................................................................178
9.3 Opgaver.......................................................................................................179
9.3.1 Opgave: Grafisk Matador-spil.............................................................................................179
9.4 Avanceret....................................................................................................181
9.4.1 Simple animationer.............................................................................................................181
9.4.2 Animationer med en separat tråd.......................................................................................182
9.4.3 Java2D - avanceret grafiktegning.......................................................................................182
9.4.4 Passiv versus aktiv visning.................................................................................................184
9.4.5 Fuldskærmstegning............................................................................................................185
9.4.6 Dobbeltbuffer......................................................................................................................186
10 Appletter..............................................................................187
10.1 HTML-dokumentet....................................................................................188
10.2 Javakoden.................................................................................................188
10.3 Metoder i appletter...................................................................................189
10.3.1 Metoder i appletter, som du kan kalde..............................................................................189
10.3.2 Metoder i appletter, som systemet kalder.........................................................................190
10.3.3 Eksempel..........................................................................................................................190
10.4 Resumé......................................................................................................191
10.5 Avanceret..................................................................................................192
10.5.1 Sikkerhedsbegrænsninger for appletter............................................................................192
10.5.2 Pakker og CODE/CODEBASE i HTML-koden..................................................................192
10.5.3 Begrænsninger i ældre netlæsere....................................................................................192
11 Grafiske standardkomponenter........................................193
11.1 Generering med et værktøj......................................................................194
11.1.1 Interaktive programmer.....................................................................................................196
11.1.2 Genvejstaster....................................................................................................................197
11.2 Overblik over komponenter.....................................................................198
11.2.1 JLabel...............................................................................................................................198
11.2.2 JButton..............................................................................................................................198
11.2.3 JCheckBox og JRadioButton............................................................................................198
11.2.4 JTextField.........................................................................................................................199
11.2.5 JTextArea.........................................................................................................................199
11.2.6 JComboBox......................................................................................................................199
11.2.7 JList..................................................................................................................................200
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11.3 Eksempel...................................................................................................200
11.4 Overblik over containere.........................................................................202
11.4.1 JWindow...........................................................................................................................202
11.4.2 JDialog..............................................................................................................................202
11.4.3 JFrame..............................................................................................................................202
11.4.4 JPanel...............................................................................................................................202
11.4.5 JApplet..............................................................................................................................202
11.4.6 JTabbedPane...................................................................................................................203
11.5 Layout-managere......................................................................................203
11.5.1 Ingen styring (null-layout).................................................................................................203
11.5.2 FlowLayout.......................................................................................................................203
11.5.3 BorderLayout....................................................................................................................204
11.5.4 GridBagLayout..................................................................................................................205
11.6 Menuer.......................................................................................................206
11.7 Test dig selv..............................................................................................208
11.8 Resumé......................................................................................................208
11.9 Avanceret..................................................................................................209
11.9.1 HTML-kode i komponenter...............................................................................................209
11.9.2 Flertrådet komponentprogrammering...............................................................................210
11.9.3 Brug af komponenter vs. paintComponent().....................................................................210
12 Interfaces - grænseflader til objekter...............................211
12.1 Definere et interface.................................................................................212
12.2 Implementere et interface........................................................................212
12.2.1 Variabler af type Tegnbar.................................................................................................213
12.2.2 Eksempler med interfacet Tegnbar...................................................................................213
12.2.3 Visning af nogle Tegnbare objekter..................................................................................215
12.2.4 Polymorfi...........................................................................................................................216
12.3 Interfaces i standardbibliotekerne..........................................................216
12.3.1 Sortering med en Comparator..........................................................................................216
12.3.2 Flere tråde med Runnable................................................................................................217
12.3.3 Lytte til musen med MouseListener..................................................................................217
12.4 Test dig selv..............................................................................................218
12.5 Resumé......................................................................................................218
12.6 Opgaver.....................................................................................................218
12.7 Avanceret..................................................................................................219
12.7.1 Collections - ArrayList's familie.........................................................................................219
12.7.2 Implementere flere interfaces...........................................................................................219
12.7.3 At udbygge interfaces.......................................................................................................220
12.7.4 Multipel arv.......................................................................................................................220
12.7.5 Variabler i et interface.......................................................................................................220
12.7.6 Statisk import....................................................................................................................220
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