Objektorienteeritud programmeerimine
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- Prudence Hamilton
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1 Objektorienteeritud programmeerimine 10. loeng, 16. aprill Marina Lepp 1
2 Eelmisel nädalal Loeng vood Lisapraktikum Praktikum sündmused Künnipäev (12.04) 2
3 Umbes mitu tundi tegelesite eelmisel nädalal selle ainega (loeng+praktikum+iseseisvalt)? tundi tundi tundi tundi tundi tundi tundi 8. üle 14 tunni 0-2 tundi 55% 23% 14% 4% 2-4 tundi 4-6 tundi 6-8 tundi 8-10 tundi 3% 0% 0% 0% tundi tundi üle 14 tunni 3
4 Kuivõrd olete selle ainega graafikus? 1. Isegi ees 2. Täiesti graafikus 3. Veidi maas, aga saan ise hakkama 4. Kõvasti maas, vajan abi 5. Ei oska öelda 43% 0% Isegi ees Täiesti graafikus 33% 21% 3% Veidi maas, aga saan ise... Kõvasti maas, vajan abi Ei oska öelda 4
5 Täna Vood Erindid 5
6 Voog (ingl. stream) osa lihtsalt kannab andmeid, osa ka töötleb ühendatakse Java I/O süsteemi abil füüsilise seadmega ühel pool tootja (allikas), teisel pool tarbija voo andmetele juurdepääs järjestikune 6
7 Jaotus Java seisukohalt jagunevad vood: sisendvoog (input stream) ja väljundvoog (output stream) vastavalt rollile "tootja-tarbija" suhtes baidivoog (byte stream) ja märgivoog (character stream) vastavalt andmete tüübile puhverdatud (buffered) ja puhverdamata voog efektiivsuse kaalutlustel puhverdada vastavalt voo kandjale failivoog (file stream) massiivivoog (array stream) toruvoog (piped stream) 7
8 Abstraktne Baidivoog InputStream FileInputStream AudioInputStream FilterInputStream DataInputStream ObjectInputStream OutputStream FileOutputStream PipedOutputStream FilterOutputStream DataOutputStream PrintStream ObjectOutputStream üks bait korraga binaarandmed (nt.class-failid) masinale orienteeritud 8
9 Baidivoog, failide kopeerimine InputStream sisse = new FileInputStream("pilt.png"); OutputStream välja = new FileOutputStream("koopia.png"); int c; // omistamine ja kontroll kombineeritud! while ((c = sisse.read())!= -1) { välja.write(c); //vood tuleb alati kinni panna sisse.close(); välja.close(); 9
10 Baidivoog, failide kopeerimine, v.2 InputStream sisse = new FileInputStream("pilt.png"); OutputStream välja = new FileOutputStream("koopia.png"); byte[] puhver = new byte[1024]; int loetud = sisse.read(puhver); while (loetud > 0) { välja.write(puhver, 0, loetud); loetud = sisse.read(puhver); //loeme järgmise tüki //vood tuleb alati kinni panna sisse.close(); välja.close(); 10
11 Abstraktne Märgivoog Reader InputStreamReader FileReader BufferedReader Writer OutputStreamWriter FileWriter BufferedWriter PrintWriter üks märk korraga tekst (nt.java-failid) inimesele orienteeritud
12 Märgivoog, failide kopeerimine Reader sisse = new FileReader("minemine.txt"); Writer välja = new FileWriter("koopia.txt"); int c; // omistamine ja kontroll kombineeritud! while ((c = sisse.read())!= -1) { välja.write(c); //vood tuleb alati kinni panna sisse.close(); välja.close(); 12
13 Märgivoog ridahaaval Võtame ridahaaval BufferedReader readline PrintWriter print println printf "\r\n" "\r" "\n"
14 Märgivoog, failide kopeerimine, v.2 BufferedReader sisse = new BufferedReader( new FileReader("minemine.txt")); PrintWriter välja = new PrintWriter( new FileWriter("koopia.txt")); String rida = sisse.readline(); while (rida!= null) { System.out.println("lugesin voost: " + rida); välja.println(rida); rida = sisse.readline(); // loeb järgmise rea //vood tuleb alati kinni panna sisse.close(); välja.close(); 14
15 Faili lõppu juurde 15
16 Väljundmärgivoogu saab realiseerida järgmise klassi alamklassidega 1.InputStream 2.OutputStream 3.Reader 4.Writer 5. muu 43% 51% 1% 3% 1%
17 Sisendbaidivoogu saab realiseerida järgmise klassi alamklassidega 1.InputStream 2.OutputStream 3.Reader 4.Writer 5. muu 82% 15% 1% 1% 0%
18 Kas meetodi System.out.println abil saab kirjutada faili? 1. jah 2. ei 88% 12% jah ei 18
19 Klass System System.in vaikimisi klaviatuurilt System.out, System.err vaikimisi ekraanile (konsoolile) 19
20 Muudame väljundit OutputStream output = new FileOutputStream("systemout.txt"); PrintStream printout = new PrintStream(output); System.setOut(printOut); System.out.println("Tere"); 20
21 Andmete kirjutamine faili DataOutputStream dos = new DataOutputStream( new FileOutputStream("andmed.bin")); dos.writeint(25); dos.writedouble(5.22); dos.close(); Java API write, writeutf 21
22 Andmed (teadaoleva struktuuriga) failist DataInputStream dis = new DataInputStream( new FileInputStream("andmed.bin")); int n = dis.readint(); double d = dis.readdouble(); dis.close(); System.out.println ("Loeti: " + n + " ja " + d); 22
23 Veebist String aadress = " InputStream sisse = new URL(aadress).openStream(); OutputStream välja = new FileOutputStream("uus.html"); 23
24 Otsejuurdepääsuga failid RandomAccessFile Osuti (ingl pointer) näitab, millises kohas ollakse seek(long pos) 24
25 import java.io.*; public class Otsejuurde { public static void main(string[] args) throws IOException { RandomAccessFile raf = new RandomAccessFile("raf.dat", "rw"); raf.writedouble(3.1415); raf.writeint(25); raf.writedouble(2.7182); raf.seek(0); System.out.println(raf.readDouble() + " " + raf.readint()); Otsejuurdepääsuga failid raf.seek(8); System.out.println(raf.readInt()); Aga 6?
26 Mis ilmub ekraanile? 1.A 2.B 3.A B 4. mitte midagi 5. muu OutputStream output = new FileOutputStream("a.txt"); PrintStream printout = new PrintStream(output); System.setOut(printOut); System.out.println("A"); System.out.println("B"); 0% 2% 37% 55% 6%
27 Mis ilmub ekraanile? 1.A 2.B 3.A B 4. mitte midagi 5. muu PrintStream vana = System.out; OutputStream output = new FileOutputStream("a.txt"); PrintStream printout = new PrintStream(output); System.setOut(printOut); System.out.println("A"); System.setOut(vana); System.out.println("B"); 85% 5% 3% 3% 3%
28 Mis ilmub ekraanile? mitte midagi 6. muu RandomAccessFile raf = new RandomAccessFile("raf.dat", "rw"); raf.writeint(9); raf.writeint(4); raf.writeint(12); raf.writeint(18); raf.seek(12); System.out.println(raf.readInt()); 7% 2% 34% 33% 9% 16%
29 Objektid Olid võimalused algtüüpide jaoks int, double, boolean Objektid? ObjectOutputStream oos = new ObjectOutputStream( new FileOutputStream("o.dat")); oos.writeobject(new int[] {1, 2, 3, 4, 5); oos.close(); ObjectInputStream ois = new ObjectInputStream( new FileInputStream("o.dat")); int[] a = (int[])ois.readobject(); ois.close();
30 Teeme ise klassi public class SKlass { String s; int i; double d; public SKlass(String s, int i, double d) { this.s = s; this.i = i; this.d = d; public String tostring() { return "s=" + s + "; i=" + i + "; d=" + d; 30
31 Proovime isendi faili saata SKlass sk = new SKlass("A", 1, 1.5); ObjectOutputStream oos = new ObjectOutputStream( new FileOutputStream ("o.dat")); oos.writeobject(sk); oos.close(); java.io.notserializableexception 31
32 Liides Serializable Java väljundvoogu saab kirjutada vaid neid objekte, mis realiseerivad liidest Serializable. Neid objekte nimetatakse serialiseeritavateks. Serialiseerimine andmejadana esitamine Liides Serializable ei ole meetodeid ega muutujaid kasutatakse vaid märkimiseks, et vastavat objekti on võimalik saata voogu Massiiv on serialiseeritav, kui tema kõik liikmed realiseerivad liidest Serializable Algtüüpidele vastavad mähisklassid realiseerivad liidest Serializable 32
33 Realiseerime liidese import java.io.serializable; public class SKlass implements Serializable { String s; int i; double d; public SKlass(String s, int i, double d) { this.s = s; this.i = i; this.d = d; public String tostring() { return "s=" + s + "; i=" + i + "; d=" + d; 33
34 Liides Serializable Saab anda indeksi Kui klass realiseerib liidest Serializable, siis kõik tema alamklassid on serialiseeritavad Kui klass realiseerib liidest Serializable, kuid sisaldab liikmeid, mis ei realiseeri liidest Serializable, siis isendit ei saa kirjutada väljundvoogu Mitteserialiseeritavate liikmete ignoreerimiseks tuleb kasutada piiritlejat transient Milleks? Midagi ajutisemat, mida pole mõtet alles hoida Kuidas? public class Klass implements Serializable { private int v1; private static double v2; private transient A v3 = new A(); 34
35 Kes need on? Dan Eliasson Generaldirektör, Myndigheten för samhällsskydd och beredskap Чечоткін Микола Олександрович Голова, Державна служба з надзвичайних ситуацій Пучков, Владимир Андреевич министр по делам гражданской обороны, чрезвычайным ситуациям и ликвидации последствий стихийных бедствий William B. Brock Long Administrator of the Federal Emergency Management Agency 35
36 Hädaolukorra seadus 1. Seaduse reguleerimisala (1)... Käesolev seadus reguleerib ka eriolukorra väljakuulutamist, lahendamist ja lõpetamist 24. Eriolukorra juht (1) Eriolukorra väljakuulutamisel määrab Vabariigi Valitsus ühe ministri, kes juhib ja koordineerib eriolukorra väljakuulutamise põhjustanud hädaolukorra lahendamist (edaspidi eriolukorra juht). 36
37 Erind? 1. Asula Albaania lõunaosas 2. India poliitik, parlamendi alamkoja liige 3. Programmi töö käigus tekkida võiv selline eriolukord, mis ei pruugi tingimata olla saatuslik programmi edasisele täitmisele
38 Näide import java.io.file; import java.util.scanner; public class Loeng10{ public static void main(string[] args) { File file = new File("andmed.txt"); Scanner sc = new Scanner(file); Information: java: Errors occured while compiling module 'Loeng10' Error:(6, 26) java: unreported exception java.io.filenotfoundexception; must be caught or declared to be thrown 38
39 Milleks? Loeme andmed failist sisse Aga kui faili polegi? Eriolukord nõuab teistsugust lähenemist Tava- ja eriolukorra kood eraldatud 39
40 Faili ei eksisteeri Eriolukorrad Faili ei saa kirjutada/lugeda Nulliga jagamine Järjendist vale indeksiga elemendi küsimine Ja veel palju teisi 40
41 Kas kompileerub? public class ErindiTest { public static void main(string[] args) { System.out.println(1/0); 1. Jah 2. Ei 78% 22%
42 Kompileerub, aga tööle ei hakka public class ErindiTest { public static void main(string[] args) { System.out.println(1/0); 42
43 Kas kompileerub? public class ErindiTest { public static void main(string[] args) { int[] arvud = {3, 7, 8; System.out.println(arvud[3]); 1. Jah 2. Ei 61% 39%
44 Kompileerub, aga tööle ei hakka public class ErindiTest { public static void main(string[] args) { int[] arvud = {3, 7, 8; System.out.println(arvud[3]); 44
45 Eriolukorrad Javas Tõrked (Throwable) vead (Error) erindid (Exception) mittekontrollitavad (RuntimeException) kontrollitavad (kompilaator leiab)
46 Throwable Error Exception LinkageError VirtualMachineError IOException MingiErind RuntimeException FileNotFoundException ArithmeticException NullPointerException IndexOutOfBoundsException mittekontrollitavad (RuntimeException) kontrollitavad (kompilaator leiab) 46
47 Eriolukorra lahendamine Lahendame probleemi kohapeal (erindi püüdmine) try { /* KOOD */ catch (Exception e){ /* LAHENDUS */ Suuname erindi edasi throws Exception{/*...*/ 47
48 Erindi püüdmata jätmine Kui erindit kinni ei püüa, siis püüab Java käituskeskkond ise Kontrollitavad erindid tuleb ise kinni püüda Mittekontrollitavaid erindeid (RuntimeException) ei pea ise kinni püüdma 48
49 Kontrollitavate ja mittekontrollitavate Kontrollitav erind erindite erinevused programm ei kompileeru, kui erindiga ei ole tegeletud throws Exception try-catch Mittekontrollitav erind programm kompileerub, aga tööle ei hakka
50 Kas Pärast ohtu ilmub ekraanile? public static void main(string[] args) { int[] arvud = {3, 7, 8; System.out.println(arvud[3]); System.out.println("Pärast ohtu"); 1. Jah 2. Ei 78% 22%
51 Kas Pärast ohtu ilmub ekraanile? public static void main(string[] args) { try { int[] arvud = {3, 7, 8; System.out.println(arvud[3]); catch (ArrayIndexOutOfBoundsException e) { //e.printstacktrace(); System.out.println("Pärast ohtu"); 1. Jah 2. Ei 82% 18%
52 Katsendidirektiiv try { /* Veaohtlik kood */ catch(erind1 e) { /* Erind1 püünis */ catch(erind2 e) { /* Erind2 püünis */ finally { /* Epiloog */ 52
53 Katsendidirektiiv try { /* Veaohtlik kood */ catch(erind1 Erind2 e) { /* Erind1 püünis ja */ /* Erind2 püünis koos */ finally { /* Epiloog */ 53
54 Katsendidirektiiv (voo sulgemisega) try(voog voog = new Voog()) { /* Veaohtlik kood */ catch(erind1 Erind2 e) { /* Erind1 püünis ja */ /* Erind2 püünis koos */ finally { /* Epiloog */ 54
55 Katsendidirektiiv (voo sulgemisega) try( Voog voog = new Voog(); Voog voog2 = new Voog() ) { /* Kood */ 55
56 Baidivoog, failide kopeerimine InputStream sisse = new FileInputStream("pilt.png"); OutputStream välja = new FileOutputStream("koopia.png"); int c; // omistamine ja kontroll kombineeritud! while ((c = sisse.read())!= -1) { välja.write(c); //vood tuleb alati kinni panna sisse.close(); välja.close(); 56
57 Baidivoog, failide kopeerimine, voo sulgemisega try ( InputStream sisse = new FileInputStream("pilt.png"); OutputStream välja = new FileOutputStream("koopia.png"); ) { int c; while ((c = sisse.read())!= -1) { välja.write(c); 57
58 Eriolukorras Pooleli jäänud töö käigus võib-olla muudeti muutujate väärtuseid avati vooge Erindi püüdmisel tuleb taastada normaalne seisund avatud vood sulgeda 58
59 Püünis (catch) Püüab kas ühe või mitu erindit Mitme erindi puhul ebavajalikud erindid keelatud Mitu püünist ühes katsendidirektiivis Ebavajalikud püünised keelatud 59
60 Throwable Error Exception LinkageError VirtualMachineError IOException MingiErind RuntimeException FileNotFoundException ArithmeticException NullPointerException IndexOutOfBoundsException mittekontrollitavad (RuntimeException) kontrollitavad (kompilaator leiab) 60
61 Mis ilmub ekraanile? try { System.out.println(1/0); int[] arvud = {3, 7, 8; System.out.println(arvud[3]); catch (ArrayIndexOutOfBoundsException e) { System.out.println("Indeks"); catch (ArithmeticException e) { System.out.println("Aritmeetika"); 1. Indeks 2. Aritmeetika 3. Indeks Aritmeetika 4. Aritmeetika Indeks 5. Midagi muud 44% 27% 19% 11% 0%
62 Mis ilmub ekraanile? try { System.out.println(1/0); int[] arvud = {3, 7, 8; System.out.println(arvud[3]); catch (RuntimeException e) { System.out.println("Käitusaegne"); catch (ArithmeticException e) { System.out.println("Aritmeetika"); 1. Käitusaegne 2. Aritmeetika 3. Käitusaegne Aritmeetika 4. Aritmeetika Käitusaegne 5. Midagi muud exception java.lang.arithmeticexception has already been caught 70% 19% 8% 2% 2%
63 Mis ilmub ekraanile? try { int[] arvud = {3, 7, 8; System.out.println(arvud[3]); System.out.println(1/0); catch (ArithmeticException e) { System.out.println("Aritmeetika"); catch (RuntimeException e) { System.out.println("Käitusaegne"); 1. Käitusaegne 2. Aritmeetika 3. Käitusaegne Aritmeetika 4. Aritmeetika Käitusaegne 5. Midagi muud 68% 20% 7% 2% 3%
64 Katsendidirektiivid Tavaline katsendidirektiiv Peab olema kas finally või vähemalt 1 catch try catch try catch catch try catch finally try catch catch finally try finally Voo sulgemisega katsendidirektiiv Ei pea olema ei finally ega catch 64
65 Katsendidirektiivid (voo sulgemisega) Tegelikult mitte tingimata voo sulgemine, vaid klassi, mis realiseerib liidest AutoCloseable Kutsutakse välja liidese AutoCloseable meetod close() 65
66 // Teeme ise suletava objekti class Suletav implements AutoCloseable { Suletav(){ System.out.println("Konstruktori public void close() { System.out.println("Sulgesin ennast!"); // Try ilma püüniseta? try(suletav suletav = new Suletav()){ System.out.println("Try sees"); Konstruktori sees Try sees Sulgesin ennast! 66
67 Epiloog (finally) Täidetakse alati (kui katsendidirektiivini jõuti ning kui JVM ja vastav lõim veel töötavad) Isegi, kui tekkis erind, mida kinni ei püütud Isegi, kui jõuti return-lauseni 67
68 Kui try-osas tekib erind, siis kõik try-osa käsud, mis asuvad peale seda, jäävad läbi vaatamata Kui try-osas erindeid ei teki, siis catch-osa juurde ei mindagi ja minnakse finally-osa juurde (kui see on olemas) ja siis minnakse nende käskude juurde, mis asuvad peale try-catch-finally Kui try-osas tekib erind ja on olemas vastav (esimene sobiv) catch-osa, siis minnakse sinna, siis minnakse finally-osa juurde (kui see on olemas) ja siis minnakse nende käskude juurde, mis asuvad peale try-catchfinally Kui try-osas tekib erind ja ei ole vastavat catch-osa, siis minnakse finally-osa juurde (kui see on olemas) ja lõpetatakse meetodi (programmi) tööd
69 Milline on täitmise järjekord, kui erindeid ei teki? try { // 1 kood, mis võib tekitada erindi // 2 catch (IOException e) { // 3 kood, mis võib tekitada erindi // 4 finally { // 5 // , 2, 3, 4, 5, , 3, 4, 5, , 2, 5, , 3, , 5 6. Mingi muu 81% 6% 4% 3% 4% 1%
70 Milline on täitmise järjekord, kui põhiplokis tekib erind, mida (selles programmis) ei püüta? try { // 1 kood, mis võib tekitada erindi // 2 catch (IOException e) { // 3 kood, mis võib tekitada erindi // 4 finally { // 5 // , 2, 3, 4, 5, , 3, 4, 5, , 2, 5, , 3, , 5 6. Mingi muu 60% 25% 6% 3% 5% 0%
71 Milline on täitmise järjekord, kui põhiplokis tekib erind, mis püütakse ja püünis ei tekita erindit? try { // 1 kood, mis võib tekitada erindi // 2 catch (IOException e) { // 3 kood, mis võib tekitada erindi // 4 finally { // 5 // , 2, 3, 4, 5, , 3, 4, 5, , 2, 5, , 3, , 5 6. Mingi muu 84% 5% 5% 5% 2% 0%
72 Milline on täitmise järjekord, kui põhiplokis tekib erind, mis püütakse ja püünises tekib ka erind? try { // 1 kood, mis võib tekitada erindi // 2 catch (IOException e) { // 3 kood, mis võib tekitada erindi // 4 finally { // 5 // , 2, 3, 4, 5, , 3, 4, 5, , 2, 5, , 3, , 5 6. Mingi muu 83% 15% 0% 0% 0% 2%
73 Katsendidirektiivid üksteise sees try { try { catch (Exception e) { catch (Exception e) { try { catch (Exception e) { finally { try { catch (Exception e) { 73
74 Katsendidirektiivid üksteise sees Kui sisemises katsendidirektiivis pole sobivat püünist, siis otsitakse püünist teda sisaldavast katsendidirektiivist Otsing jätkub kuni sobiva leidmiseni või kuni katsendidirektiivide lõppemiseni 74
75 Katsendi- või tingimusdirektiiv if(a.length > 0) { System.out.println(a[0]); else { või try {System.out.println(a[0]); catch (IndexOutOfBoundsException e){ 75
76 Loengu tempo oli 1. liiga kiire 2. paras 3. liiga aeglane 83% 13% 4% liiga kiire paras liiga aeglane 76
77 Materjal tundus 1. liiga lihtne 2. parajalt jõukohane 3. liiga keeruline 91% 1% 8% liiga lihtne parajalt jõukohane liiga keeruline 77
78 Suur tänu osalemast! Kohtumiseni! 78
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