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2 extends (*) (*) extend extends 2

3 class Person { private String name; String name() {return name; Person(String name) { this.name=name; class Worker extends Person { private int salary; Worker(String name, int salary) { super(name); // this.salary = salary; int salary() {return salary; // String who() { return "I am a worker, "+name(); // 3

4 (RDB) entitiy-relationship diagram with ISA ISA = extends 4

5 Integer java.lang java.lang.object +--java.lang.number +--java.lang.integer : Comparable, Serializable ArrayList java.util java.lang.object +--java.util.abstractcollection +--java.util.abstractlist +--java.util.arraylist : Cloneable, Collection, List, RandomAccess, Serializable 5

6 vs Java 6

7 2 7

8 3 CopyC DummyC CopyC class C { private int x; C(int x) {this.x=x; double divide(int y) { return (double)x/y; public static void main(string[] args) { C a = new C(3); System.out.println(a.divide(2)); abstract class CopyC { private int x; CopyC(int x) {this.x=x; double divide(int y) { return (double)x/y; class DummyC extends CopyC { DummyC(int x) {super(x); public static void main(string[] args) { DummyC a = new DummyC(3); System.out.println(a.divide(2)); 8

9 (abstract) class C c extends C p 9

10 class Company { private Employee[] emplist; // FullTime ParTime Company(Employee[] emplist) {this.emplist=emplist; int sumofsalary() { int total = 0; for (int i=0;i<emplist.length;i++) total += emplist[i].salary(); // salary() return total; public static void main(string[] args) { Employee[] emplist = {new FullTime("yoshiko", 10000), new PartTime("taro", 10,30); System.out.println("total = "+(new Company(emplist)).sumOfSalary()); abstract class Employee {// private String name; Employee(String name) {this.name=name;// // // abstract int salary(); // class FullTime extends Employee { private int salary; FullTime(String name, int salary) {// super(name); this.salary = salary; int salary() {return salary; // FullTime // public must be public class PartTime extends Employee { private int hourperday, paymentforhour; PartTime(String name, int hourperday, int paymentforhour) {//PartTime super(name); this.hourperday=hourperday; this.paymentforhour=paymentforhour; int salary() { return hourperday*paymentforhour*20; 10

11 class Company { private Employee[] emplist; int sumofsalary() { int total = 0; for (int i=0;i<emplist.length;i++) total += emplist[i].salary(); return total; interface HasSalary { int salary(); // abstract class Employee implements HasSalary{/* HasSalary */ public abstract int salary(); /* public int salary() {... */ // name // class FullTime extends Employee { private int salary; public int salary() {return salary;//public class PartTime extends Employee { private int hourperday, paymentforhour; public int salary() { return hourperday*paymentforhour*20;//5days/week, 4 week 11

12 single inheritance or multiple inheritance? class C extends P user Object: Object interface IC extends IP 12

13 abstract class Employee { abstract void hellow(); abstract int salary(); class FullTime extends Employee { private int salary; void hellow() {System.out.println( "Hellow, I am a full time worker"); int salary() {return salary; class Employee { void hellow() { // do nothing int salary() {return -1;// nonsense class FullTime extends Employee { private int salary; void hellow() {System.out.println( "Hellow, I am a full time worker"); int salary() {return salary; Employee hellow salary Employee hellow salary 13

14 3.1 extends class P { int x = 1; class C extends P{ int y = 2; // C(int x, int y) { // this.x=x; this.y=y; C(int y) { // this.y=y; C() { // void show() { System.out.println("x="+x+", y="+y); public static void main(string[] args) { (new C()).show(); (new C(200)).show(); (new C(100,200)).show(); /* x=1, y=2 x=1, y=200 x=100, y=200 */ C this.x=x; x top class Object 14

15 class P { private int x; int getx() {return x; P(int x) {this.x = x; class C extends P { private int y; // C(int x, int y) { super(x); this.y=y; void show() { System.out.println( "x="+getx()+", y="+y); public static void main(string[] args) { (new C(100,200)).show(); Read super(int) int x void setx(int x) {this.x=x; C(int x, int y) { this.setx(x); this.y=y; P(int) (*) (*) P() P() { 15

16 generic Object java.util.arraylist capacity generic ArrayList ArrayList<String> abc ArrayList String LinkedList import java.util.arraylist; class Afo { public static void main(string args[]){ ArrayList<String> slist = new ArrayList<String>(); slist.add("abc"); System.out.println(slist.get(0)); // ArrayList list = new ArrayList(); // arraylist of object list.add("abc"); // String str = slist.get(0); // compile error. slist.get(0) object String str1 = (String)list.get(0); // System.out.println(str1); 16

17 generic type import java.util.arraylist; interface Showable { void show(); interface SortableObj extends Showable { String name(); int code(); abstract class Sorter { abstract boolean lessthan(sortableobj x, SortableObj y); abstract boolean equals(sortableobj x, SortableObj y); void swap(arraylist<sortableobj> inputdata) {// if (lessthan(inputdata.get(0),inputdata.get(1))) return; SortableObj tmp = inputdata.get(1); inputdata.set(1, inputdata.get(0)); inputdata.set(0, tmp); void show(arraylist<sortableobj> inputdata) { for (int i=0;i<inputdata.size();i++) inputdata.get(i).show(); System.out.println(); class SortedByCode extends Sorter{ boolean lessthan(sortableobj x, SortableObj y) {return x.code() < y.code(); boolean equals(sortableobj x, SortableObj y) {return x.code() == x.code(); class SorterByName extends Sorter{ boolean lessthan(sortableobj x, SortableObj y) {return x.name().compareto(y.name()) <0; boolean equals(sortableobj x, SortableObj y) {return x.name().compareto(x.name()) == 0; // public // // 17

18 class St implements SortableObj { private int code; public int code() {return code; private String name; public String name() {return name; public void show() {System.out.print(name+"("+code+"),"); St(int i, String name) {code = i;this.name=name; // java St code 103 katoh 101 okubo 102 saitoh // java St name 101 okubo 103 katoh 102 saitoh public static void main(string args[]){ ArrayList<SortableObj> data = new ArrayList<SortableObj>(args.length/2); for (int i=0;i<(args.length-1)/2;i++) { St st = new St(Integer.parseInt(args[2*i+1]),args[2*i+2]); data.add(st); ; Sorter sorter; if (args[0].equals("code")) sorter = new SortedByCode(); else if (args[0].equals("name")) sorter = new SorterByName(); else sorter = null;// sorter.swap(data); sorter.show(data); 18

19 C 1 ( ) C 2 ( ) (abstract) class C 1 extends C 2 interface B extends B 1,..., B k (*) (**) (abstract) class C 1 extends C 2 implements B 1,..., B k (*) (**) abstract class A implements B 19

20 τ m (σ 1 x 1,..., σ n x n ) τ m (σ 1,..., σ n ) class O3 { void f() { System.out.println("o3"); class O2 extends O3 { void f() { System.out.println("o2"); class O1 extends O2 { void f() { System.out.println("o1"); public static void main(string args[]){ O2 x = new O1(); x.f(); // (*) (*) x O2 O1 O1 f() 20

21 abstract method public (*) implements B satisfied. So, implements (**) 21

22 /* holders.holder(coin.index()): coin Holders transaction: Holders stock Holder Symbol subclass interface Symbols Symbols String name Symbols */ abstract class Symbol {// Item Coin Cancel private String name; String name() {return name; Symbol(String n) {name = n; abstract void message();// class Item extends Symbol{ private int price; int price() {return price; Item(String n, int p) {super(n); price=p; void message() {System.out.println(" "+name()+" ("+price+" ) "); class Coin extends Symbol{ private int value; int value() {return value; Coin(String name, int v) {super(name); value=v; private int index;//holder holders int index() {return index; void setindex(int x) {index = x; void message() {System.out.println(" "+value+" "); class Cancel extends Symbol { Cancel(String n) {super(n); void message() {System.out.println(" "); 22

23 interface Symbols { Coin c10 = new Coin("c10",10), c50 = new Coin("c50",50), c100 = new Coin("c100",100), c500 = new Coin("c500",500); Coin[] coins = {c10,c50,c100,c500;// // Cancel cancel = new Cancel("cancel"); Item orangejuice = new Item("orange juice", 80), bosscoffee = new Item("boss coffee", 120), healthymilk = new Item("healthy milk", 60); Symbol[] symbols = {c10, c50, c100, c500, cancel, orangejuice, bosscoffee, healthymilk ; /* SymbolProcess VendingMachine */ ImplementationOfSymbols ios = new ImplementationOfSymbols(); Symbol stringtosymbol(string arg); void checkcoins(); class ImplementationOfSymbols implements Symbols { public Symbol stringtosymbol(string arg) { for (int j=0; j<symbols.length; j++) if (symbols[j].name().equals(arg)) return symbols[j]; System.out.println(" *** "+arg); return null; public void checkcoins() {// Symbols.coins int max = 0; for (int i=0;i<coins.length;i++) if (max < coins[i].value()) { coins[i].setindex(i); max = coins[i].value(); else { System.out.println(" *** Symbols.coins "); System.exit(1); ; 23

24 class Holder {/* stock, transaction */ private Coin coin; Coin coin() {return coin; private int nof = 0; // void count() {nof++; int nof() {return nof; void add(int x) {nof += x; void subtract(int x){nof -= x; void reset() {nof=0; int amount() {return nof * coin.value(); void returncoin(int x) { if (x == 0) return; nof -= x; System.out.println(" "+coin.value()+" "+x+" "); Holder(Coin coin) {this.coin = coin; class VendingMachine implements Symbols{ public Symbol stringtosymbol(string arg) {return ios.stringtosymbol(arg); public void checkcoins() {ios.checkcoins(); // private Holders stock, transaction; VendingMachine() { checkcoins(); stock = new Holders(); transaction = new Holders(); class Holders {// private Holder[] holders = new Holder[coins.length]; private Holders() { for (int i=0;i<coins.length;i++) holders[i] = new Holder(coins[i]); private Holder holder(coin coin) {return holders[coin.index()]; private int totalamount() { int sum = 0; for (int i=0;i<holders.length;i++) sum += holders[i].amount(); return sum; private void returnallcoin() { for (int i=0;i<coins.length;i++) holders[i].returncoin(holders[i].nof()); // end Holders 24

25 private void paybackchange(int amount) { int[] paybacknof = new int[coins.length]; for (int i=coins.length-1;i>=0;i--) { paybacknof[i] = Math.min(amount/(coins[i].value()), stock.holder(coins[i]).nof()+transaction.holder(coins[i]).nof()); amount -= paybacknof[i] * coins[i].value(); ; if (amount > 0) { System.out.println(" "); transaction.returnallcoin(); return; ; System.out.println(" "); for (int i=0;i<coins.length;i++) { stock.holder(coins[i]).add(transaction.holder(coins[i]).nof()); transaction.holder(coins[i]).reset(); stock.holder(coins[i]).returncoin(paybacknof[i]); ; void process(symbol input) { input.message(); if (input instanceof Cancel) { transaction.returnallcoin(); System.out.println("+++ "); return; ; if (input instanceof Coin) { transaction.holder((coin)input).count(); return; ; if (input instanceof Item) { int difference = ((Item)input).price()-transaction.totalAmount(); if (difference > 0) { System.out.println(" "+difference+" "); return;// ; paybackchange( -difference ); System.out.println(" ++ "); ; 25

26 int sales() {return stock.totalamount(); class test { public static void main(string args[]){ VendingMachine vm = new VendingMachine(); Symbol input; for (int i=0;i<args.length;i++) if ((input = vm.stringtosymbol(args[i]))!=null) vm.process(input); System.out.println(" ++ "+ vm.sales()); //java test c10 c10 c100 "boss coffee" c100 "orange juice" c100 "healthy milk" c1000 c50 c10 c10 "healthy milk" boss coffee (120 ) orange juice (80 ) healthy milk (60 ) *** c healthy milk (60 ) instanceof void process(symbol) instanceof Symbol instanceof instanceof 26

27 C.main interface A {int f(); class B { int g(a a) {return 100+a.f(); final class C extends B implements A { private int y; C(int y) {this.y=y; public int f() {return y; public static void main(string args[]){ C c = new C(100); System.out.println(c.g(c)); 27

28 StudentRecordForLecture, StudentRecordForExercise Lecture, Exercise StudentRecordForLecture StudentRecordForExercise Item (A1) (A2) (A3) ( ) Exercise Exercise(String, StudentRecordForExercise[]) Exercise StudentRecordForExercise ( ) double avg() Lecture Excercise

29 1. abstract class StudentRecord { 2. private String name;// 3. abstract double score(); 4. StudentRecord(String name) {this.name=name; class StudentRecordForLecture extends StudentRecord{ 7. private int score;// 8. double score() {return score; 9. StudentRecordForLecture(String name, int score) { 10. super(name); this.score = score; class StudentRecordForExercise extends StudentRecord{ 14. private static final int noftimes = 12; 15. private int[] scores; 16. StudentRecordForExercise(String name, int[] rs) { 17. super(name); scores = rs; // rs.length == // 19. double score() { 20. double sum = 0.0; 21. for (int i=0;i<noftimes;i++) sum += scores[i]; 22. return sum/noftimes; abstract class Item { 26. private String name;// 27. private StudentRecord[] records; 28. Item(String name, StudentRecord[] records) { 29. this.name = name; this.records = records; double avg() { // 32. double sum = 0.0; 33. for (int i=0; i<records.length;i++) sum += records[i].score(); 34. return sum/records.length; class Lecture extends Item { 38. Lecture(String name, StudentRecordForLecture[] records) { 39. super(name, records); class Exercise extends Item{ 43. Exercise(String name, StudentRecordForExercise[] records) { ( )

30 java A = {(a,1),(b,3),(c,2) class ArrayList extends ArrayList ArrayList public methods ( ): size(): ArrayList(): add(object x): x Object Object get(int j): j ObjectWithEquality ArrayList new MultiSet() multisetadd ObjectWithEquality public static void main(string args[]) super ArrayList add MultiSet add 30

31 import java.util.arraylist; // class ObjectWithCounter { private ObjectWithEquality value; ObjectWithEquality getvalue() {return value; private int counter=1; void countone() {counter++; int getcounter() {return counter; ObjectWithCounter(ObjectWithEquality owe) {value=owe; interface ObjectWithEquality { boolean equals(objectwithequality x); class MultiSet extends ArrayList { private int totalnumber = 0; int gettotalnumber() {return totalnumber; void multisetadd(objectwithequality owequality) { ObjectWithCounter owcounter; if (size()==0 (owcounter = checkmembership(owequality))==null ) add(new ObjectWithCounter(owEquality)); else owcounter.countone(); totalnumber++; private ObjectWithCounter checkmembership(objectwithequality owequality) { ObjectWithCounter owcounter; for (int i=0;i<size();i++) if (( owcounter = (ObjectWithCounter)get(i) ). getvalue().equals(owequality)) return owcounter; return null; 31

DVIOUT-exer

DVIOUT-exer プログラム理論と言語 : 期末試験用問題集 Part2 (2009) 演習問題 2-0 オブジェクト指向言語, とりわけ Java に関する用語の設問をもうける. 重要な語句については復習をしておくこと. 1 演習問題 2-1( レジメ記載の問題を具体化した問題 ) 下記は, 整数 (int) を要素とする線形リストのプログラムである. class IntCell { private int value