MODUL 3 : CONSTRUCTOR AND OVERLOADING

A.                Objectives

Objectives of making this report are :

1.      Students are able to understand what the definition and how to use Constructor in Java.

2.      Students are able to understan what the definition and how to use Overloading in Java.

B.                 Theoretical Basis

Constructor is a method used to give starting value when object created. This method will be callled automatically by Java when new used to create object from a class. Characteristic of constructor :

·         Name of constructor is same with name of class.

·         Constructor doesn’t have return value (included it may not present void keyword).

C.                Tools and Material

1.      Laptop

2.      Java Development Kit (JDK 8)

3.      NetBeans IDE 8.0.2

D.                Work Steps

1.      Experiment 1

a.       Creating project and Source Packages required below.

·         Project Name                           :           Modul 3

·         Source Packages Name           :           Percobaan 1

b.      Creating new java file named “Buku.java”. Typing program code below :

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class Buku {
    String pengarang;
    String judul;
    int tahunTerbit;
  
    //membuat konstruktor
    public Buku(String pengarang, String judul){
        this.judul = judul;
        this.pengarang = pengarang;
    }//akhir konstruktor
      
    //membuat method
    public void infoBuku(){
        System.out.println("Judul Buku "+judul);
        System.out.println("Pengarang "+pengarang);
        System.out.println("Tahun Terbit "+tahunTerbit);
    }
}

c.       Saving and compiling the program codes.

d.      Creating a new java class that has function main() as like program codes below.

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class OverLoadingKonstruktor {
    public static void main (String []args){
        Buku bukuku = new Buku("John","Panduan Pintar Guitar");
        bukuku.infoBuku();
    }
}

e.       Saving as the class name and compiling the program codes above. 

Object creating may not be typed as :

New Buku();

But it should be like this : 
New Buku (Parameter1, Parameter2);

2.      Experiment 2 (Constructor Overloading)

a.       Editing file of “Buku.java” by added constructor code of overloding.

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class Buku {
    String pengarang;
    String judul;
    int tahunTerbit;
   
    //membuat konstruktor
    public Buku(String pengarang, String judul){
        this.judul = judul;
        this.pengarang = pengarang;
    }//akhir konstruktor
   
    //membuat OverLoading Konstruktor
    public Buku(String pengarang, String judul, int tahunTerbit){
        this.pengarang = pengarang;
        this.judul = judul;
        this.tahunTerbit = tahunTerbit;
    }
   
    //membuat method
    public void infoBuku(){
        System.out.println("Judul Buku "+judul);
        System.out.println("Pengarang "+pengarang);
        System.out.println("Tahun Terbit "+tahunTerbit+ "\n");
    }
}

b.      Compiling the program codes.

c.       Next, creating a new class named “OverLoadingKonstruktor.java” then typing program code below.

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class OverLoadingKonstruktor {
    public static void main (String []args){
        Buku bukuku = new Buku("John","Panduan Pintar Guitar");
        Buku bukumu = new Buku("John","Panduan Pintar Guitar",2015);
        bukuku.infoBuku();
        bukumu.infoBuku();
    }
}

d.      Saving and compiling program codes above.

e.       Comparing between this result and the result before.

3.      Overloading Method

a.       Creating a new class named “Matematika.java”, typing program codes below.

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class Matematika {
    static public double kuadrat(double nilai){
        return nilai*nilai;
    }
    static public int kuadrat(int nilai){
        return nilai*nilai;
    }
    static public double kuadrat(String nilai){
        double bilangan;
        bilangan = Double.valueOf(nilai).doubleValue();
        return bilangan*bilangan;
    }
}

b.      Compiling program codes above.

c.       Then, creating a new class with function of main() below.

package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class OverloadingMethod {
    public static void main (String []args){
        System.out.println("Nilai kuadrat dari tipe data double "+Matematika.kuadrat(20));
        System.out.println("Nilai kuadrat dari tipe data integer "+Matematika.kuadrat(20));
        System.out.println("Nilai kuadrat dari tipe data Sting "+Matematika.kuadrat(20));
    }
}

d.      Saving and compiling as the file name.

E.                 Analysis

Overloading the constructor means a mechanism of constructor creation that has form more than one. In this case, distinguishing among one constructor and other constructors is a number of parameters or type of parameters.

Overloading usually used on constructor, but overloading also can be used on method of non-constructor.

F.                 Tasks

1.      Editing class of “Buku.java” and class of “OverLoadingKonstruktor.java”

2.      Program codes :

      package Percobaan1;

/**
 *
 * @author Jhonny
 */
public class OverLoadingKonstruktor {
    public static void main (String []args){
        Buku bukuku = new Buku("John","Panduan Pintar Guitar");
        Buku bukumu = new Buku("John","Panduan Pintar Guitar",2015);
        Buku bukuKita = new Buku("Sungha","Null");
        Buku bukuKami = new Buku("Jung","Panduan Pintar Komputer",2009);
      
        System.out.println("Bukuku");
        bukuku.infoBuku();
      
        System.out.println("Bukumu");
        bukumu.infoBuku();
     
        System.out.println("BukuKita");
        bukuKita.infoBuku();
      
        System.out.println("BukuKami");
        bukuKami.infoBuku();
    }
}

3.      Finally result

: