PEMROGRAMAN LANJUT

Program Teknologi Informasi & Ilmu Komputer, Universitas Brawijaya

ABSTRACT CLASS & INTERFACE

Dr. Eng. Herman Tolle

Sistem Informasi PTIIK UBSemester Genap 2014/2015

ABSTRACT

• Abstract Class (Abstraksi) adalah kelas yang memiliki satu atau lebih method yang belum didefinisikan

• Method dalam class abstract yang tidak mempunyai implementasi dinamakan method abstract.

• Untuk membuat method abstract, cukup menulis deklarasi method tanpa isi tubuh class dan digunakan menggunakan kata kunci abstract.

• Contoh: public abstract void someMethod();

ABSTRAKSI

Penggunaan class Abstract

• Class abstract dapat digunakan sebagai superclass untuk satu atau lebih sub class (kelas turunan)

• Method abstract didefinisikan pada class abstract sebagai definisi umum saja, yang harus didetailkan / diimplementasikan pada kelas turunannya.

INTERFACE

• Interface adalah sebuah blok (setingkat class) yang hanya berisi signature method dan constant (konstanta)

• Signature method dapat dianggap seperti sebuah abstract method. Method yang tidak memiliki implementasi tetapi hanya berupa nama method saja

public interface Movable { public void moveUp(); public void moveDown(); public void moveLeft(); public void moveRight(); }

public class MovablePoint implements Movable { // Private member variablesprivate int x, y; // (x, y) coordinates of the point

// Constructorpublic MovablePoint(int x, int y) { this.x = x; this.y = y; }

@Overridepublic String toString() { return "Point at (" + x + "," + y + ")"; }

// Implement abstract methods defined in the interface Movable@Override public void moveUp() { y--; } @Override public void moveDown() { y++; } @Override public void moveLeft() { x--; } @Override public void moveRight() { x++; }

}Movablepoint.class

public class TestMovable { public static void main(String[] args) { Movable m1 = new MovablePoint(5, 5); // upcast

System.out.println(m1);

m1.moveDown(); System.out.println(m1);

m1.moveRight(); System.out.println(m1); }

}

Implementasi Interface

• Menggunakan kata kunci IMPLEMENTS• public class MovablePoint implements Movable

• Class hanya dapat mengEXTEND SATU superclass, tetapi dapat mengIMPLEMENTASIkan BANYAK interface.

• Ketika class mengimplementasikan sebuah interface, selalu pastikan bahwa semua method dalam interface telah diimplementasikan semuanya pada class tsb, jika tidak, akan ada pesan kesalahan

• Line.java:4: Line is not abstract and does not override abstract

Kapan menggunakan interface?

•Kita menggunakan interface jika kita ingin class yang tidak berhubungan mengimplementasikanmethod atau fungsi-fungsi yang sama. •Melalui interface kita dapat menangkap

kemiripan diantara class yang tidak berhubungan•Sebuah Class dapat mengimplementasikan lebih

dari satu interface.

Interface Naming Convention

• Use an adjective (typically ends with "able") consisting of one or more words.

• Each word shall be initial capitalized (camel-case).

• Forexample: Serializable, Extenalizable,Movable, Clonable, Runnable, etc.

•

Pewarisan Antar Interface

• Interface bukan bagian dari hirarki class. • Interface dapat mempunyai hubungan pewarisan antara mereka

sendiri. • Contohnya, misal kita punya dua interface StudentInterface dan

PersonInterface. Jika StudentInterface meng-extend PersonInterface, maka ia akan mewariskan semua deklarasi method dalam PersonInterface.

public interface PersonInterface {. . .}

public interface StudentInterface extends PersonInterface {. . .}

Contoh Interface

public class MovableCircle extends Circle implements Movable {

private int radius;

private MovablePoint Center = new MovablePoint();

public MovableCircle(int x, int y, int xs, int ys, int R)

{

super(R);

Center.setPoint(x, y);

Center.setSpeed(xs, ys);

}

public void moveUp()

{

Center.setPoint(x, y-ys);

Center.setPoint(Center.getX(), Center.getY()-Center.getYSpeed()))

Center.moveUp();

}

Catatan

• Interface dapat diturunkan dari satu atau lebih interfaceinterface Hockey extends Sports, Event

• Class dapat mengimplement lebih dari satuinterface Class PersegiPanjang implements Relation, Movable, Resizable

17

10.8 Case Study: Creating and Using Interfaces

• Use interface Shape

– Replace abstract class Shape

• Interface

– Declaration begins with interface keyword

– Classes implement an interface (and its methods)

– Contains public abstract methods

• Classes (that implement the interface) must implement these methods

2003 Prentice Hall, Inc.

All rights reserved.

Outline18

Shape.java

Lines 5-7

Classes that

implement Shapemust implement these

methods

1 // Fig. 10.18: Shape.java

2 // Shape interface declaration.

3

4 public interface Shape {

5 public double getArea(); // calculate area

6 public double getVolume(); // calculate volume

7 public String getName(); // return shape name

8

9 } // end interface Shape

Classes that implement Shapemust implement these methods

2003 Prentice Hall, Inc.

All rights reserved.

Outline19

Point.java

Line 4

Point implements

interface Shape

1 // Fig. 10.19: Point.java

2 // Point class declaration implements interface Shape.

3

4 public class Point extends Object implements Shape {

5 private int x; // x part of coordinate pair

6 private int y; // y part of coordinate pair

7

8 // no-argument constructor; x and y default to 0

9 public Point()

10 {

11 // implicit call to Object constructor occurs here

12 }

13

14 // constructor

15 public Point( int xValue, int yValue )

16 {

17 // implicit call to Object constructor occurs here

18 x = xValue; // no need for validation

19 y = yValue; // no need for validation

20 }

21

22 // set x in coordinate pair

23 public void setX( int xValue )

24 {

25 x = xValue; // no need for validation

26 }

27

Point implements interface Shape

2003 Prentice Hall, Inc.

All rights reserved.

Outline20

Point.java

28 // return x from coordinate pair

29 public int getX()

30 {

31 return x;

32 }

33

34 // set y in coordinate pair

35 public void setY( int yValue )

36 {

37 y = yValue; // no need for validation

38 }

39

40 // return y from coordinate pair

41 public int getY()

42 {

43 return y;

44 }

45

2003 Prentice Hall, Inc.

All rights reserved.

Outline21

Point.java

Lines 47-59

Implement methods

specified by interface

Shape

46 // declare abstract method getArea

47 public double getArea()

48 {

49 return 0.0;

50 }

51

52 // declare abstract method getVolume

53 public double getVolume()

54 {

55 return 0.0;

56 }

57

58 // override abstract method getName to return "Point"

59 public String getName()

60 {

61 return "Point";

62 }

63

64 // override toString to return String representation of Point

65 public String toString()

66 {

67 return "[" + getX() + ", " + getY() + "]";

68 }

69

70 } // end class Point

Implement methods specified

by interface Shape

2003 Prentice Hall, Inc.

All rights reserved.

Outline22

InterfaceTest.java

Line 23

Create Shape array

1 // Fig. 10.20: InterfaceTest.java

2 // Test Point, Circle, Cylinder hierarchy with interface Shape.

3 import java.text.DecimalFormat;

4 import javax.swing.JOptionPane;

5

6 public class InterfaceTest {

7

8 public static void main( String args[] )

9 {

10 // set floating-point number format

11 DecimalFormat twoDigits = new DecimalFormat( "0.00" );

12

13 // create Point, Circle and Cylinder objects

14 Point point = new Point( 7, 11 );

15 Circle circle = new Circle( 22, 8, 3.5 );

16 Cylinder cylinder = new Cylinder( 20, 30, 3.3, 10.75 );

17

18 // obtain name and string representation of each object

19 String output = point.getName() + ": " + point + "\n" +

20 circle.getName() + ": " + circle + "\n" +

21 cylinder.getName() + ": " + cylinder + "\n";

22

23 Shape arrayOfShapes[] = new Shape[ 3 ]; // create Shape array

24

Create Shape array

2003 Prentice Hall, Inc.

All rights reserved.

Outline23

InterfaceTest.java

Lines 36-42

Loop through

arrayOfShapes to

get name, string

representation, area

and volume of every

shape in array.

25 // aim arrayOfShapes[ 0 ] at subclass Point object

26 arrayOfShapes[ 0 ] = point;

27

28 // aim arrayOfShapes[ 1 ] at subclass Circle object

29 arrayOfShapes[ 1 ] = circle;

30

31 // aim arrayOfShapes[ 2 ] at subclass Cylinder object

32 arrayOfShapes[ 2 ] = cylinder;

33

34 // loop through arrayOfShapes to get name, string

35 // representation, area and volume of every Shape in array

36 for ( int i = 0; i < arrayOfShapes.length; i++ ) {

37 output += "\n\n" + arrayOfShapes[ i ].getName() + ": " +

38 arrayOfShapes[ i ].toString() + "\nArea = " +

39 twoDigits.format( arrayOfShapes[ i ].getArea() ) +

40 "\nVolume = " +

41 twoDigits.format( arrayOfShapes[ i ].getVolume() );

42 }

43

44 JOptionPane.showMessageDialog( null, output ); // display output

45

46 System.exit( 0 );

47

48 } // end main

49

50 } // end class InterfaceTest

Loop through arrayOfShapes to

get name, string representation, area

and volume of every shape in array

2003 Prentice Hall, Inc.

All rights reserved.

Outline24

InterfaceTest.java

Contoh Kasus

• Ada 2 class: class Line dan class MyInteger

• class Line berisi method yang menghitung panjang dari garis dan membandingkan object Line ke object dari class yang sama.

• Class MyInteger berisi method yang membandingkan object MyInteger ke object dari class yang sama.

• Kedua class mempunyai method yang hampir sama, yaitu memperbandingkan dua object lain dalam tipe yang sama.

• Supaya dapat menjalankan cara untuk memastikan bahwa dua class-class ini mengimplementasikan beberapa method dengan fungsi yang sama, kita dapat menggunakan sebuah interface

• untuk hal ini. Kita dapat membuat sebuah class interface, katakanlah interface Relation dimana mempunyai deklarasi method untuk fungsi-fungsi pembandingan.

public interface Relation{public boolean isGreater( Object a, Object b);public boolean isLess( Object a, Object b);public boolean isEqual( Object a, Object b);}

public class Line implements Relation{private double x1;private double x2;private double y1;private double y2;private String nama;

public Line(double x1, double x2, double y1, double y2, String name){

this.x1 = x1;this.x2 = x2;this.y1 = y1;this.y2 = y2; this.nama = name;

}

public double getLength(){double length = Math.sqrt((x2-x1)*(x2-x1) +

(y2-y1)* (y2-y1));return length;

}

public boolean isGreater( Object a, Object b){double aLen = ((Line)a).getLength();double bLen = ((Line)b).getLength();return (aLen > bLen);

}public boolean isLess( Object a, Object b){double aLen = ((Line)a).getLength();double bLen = ((Line)b).getLength();return (aLen < bLen);

}public boolean isEqual( Object a, Object b){double aLen = ((Line)a).getLength();double bLen = ((Line)b).getLength();return (aLen == bLen);

}}

Latihan

• Buat Class MyInteger yang mengimplementasikan penggunaan interface Relation

• Buat class MovableCircle yang mengimplementasi interface movable

Latihan

1. Buat Kode Program untuk menentukan mana garis terpanjang dan mana garis terpendek dari input 3 buah objek garis (Line)

2. Buat Class dan Program seperti kasus di atas untuk objek Persegi Panjang (atribut: X1, X2, Y1, Y2)

Catatan: soal no 2 dikerjakan dan dikumpulkan

File 1: Relation.javaFile 2: Line.javaFile 3: TestLine.java

// file 3: TestLine.javapublic static void main() {Line LineA = new Line(3,7,8,4,”GarisA”);Line LineB = new Line(-2,2,2,-2,”GarisB”);Line LineC = new Line(10,13,3,-2,”GarisC”);Line Max = new Line(0,0,0,0,”max”);Max = LineA;If Max.isGreater(LineB, Max)

Max = LineB;If Max.isGreater(LineC, Max)

Max = LineC;System.out.println(“Garis terpanjang adalah = “ +

Max.getName());}

Latihan F

1. Buat Kode Program untuk menentukan mana garis terpanjang dan mana garis terpendek dari input 3 buah objek garis (Line)

2. Buat Class dan Program seperti kasus di atas untuk objek Persegi Panjang (atribut: X1, X2, Y1, Y2), mencari objek TERLUAS dari input 3 buah objek Persegi

Catatan: soal no 2 dikerjakan dan dikumpulkan

33

10.8 Case Study: Creating and Using Interfaces (Cont.)

• Implementing Multiple Interface

– Provide common-separated list of interface names after keyword implements

• Declaring Constants with Interfaces

– public interface Constants {public static final int ONE = 1;public static final int TWO = 2;public static final int THREE =

3;}

34

10.10 Type-Wrapper Classes for Primitive Types

• Type-wrapper class

– Each primitive type has one

• Character, Byte, Integer, Boolean, etc.

– Enable to represent primitive as Object

• Primitive types can be processed polymorphically

– Declared as final

– Many methods are declared static

Class BuahCatur

-PosX: int;-PosY: int;-Warna: String;

Class Pion extends BuahCatur implements ChessMove

-PosXAwal: int;-PosYAwal: int;

+Pion( String W, int X, int Y)+MoveUp(int);+MoveDown(int)

ChessMove<<interface>>

Move(int);MoveUp(int);MoveDown(int);

BuahCatur Pion1 = new Pion (“White”, 1, 2);Pion1.MoveUp(1);Benteng B1 = new Benteng(“White”, 1, 1);B1.MoveUp(5);

Pion1 = new Benteng(“White”, 1,8);

Pion1.MoveDown(3);