Mengenal Perintah Java (Scanner dan Library)

Scanner
Scanner merupakan perintah untuk membuat objek atau menginisialisasi object yang diinginkan pengguna atau yang diinputkan pengguna.
Contoh source code :

 /**  
  * Write a description of class Account here.  
  *   
  * @author Nirmala  
  * @version 03  
  */  
 public class Account  
 {  
   private double Balance;  
   public Account(double initialBalance)  
   {  
     if(initialBalance>0.0)  
       Balance=initialBalance;  
   }  
   public void credit(double amount)  
   {  
     Balance=Balance+amount;  
   }  
   public double getBalance()  
   {  
     return Balance;  
   }  
 } 

 /**  
  * Write a description of class AccountTest here.  
  *   
  * @author Nirmala  
  * @version (a version number or a date)  
  */  
 import java.util.Scanner;  
 public class AccountTest  
 {  
   public static void main(String[] args)  
   {  
     Account account1=new Account(50.00);  
     Account account2=new Account(-7.53);  
     System.out.printf("account1 balance: $%.2f\n", account1.getBalance());  
     System.out.printf("account2 balance: $%.2f\n\n", account2.getBalance());  
     Scanner input=new Scanner(System.in);  
     double depositAmount;  
     System.out.print("Enter deposit amount for account1: ");  
     depositAmount=input.nextDouble();  
     System.out.printf("\nadding %.2f to account1 balance\n\n",  
       depositAmount );  
     account1.credit(depositAmount);  
     System.out.printf("Enter deposit amount for account2: ");  
     depositAmount=input.nextDouble();  
     System.out.printf("\nadding %.2f to account2 balance\n\n",  
       depositAmount);  
     account2.credit(depositAmount);  
     System.out.printf("account1 balance: $%.2f\n",  
       account1.getBalance());  
     System.out.printf("account2 balance: $%.2f\n",  
       account2.getBalance());  
   }  
 }  

Output :


Library
Library adalah sekumpulan package atau koleksi kelas yang telah disediakan oleh Java. Untuk menggunakan Library dalam java kita menggunakan syntax import. Syntax import digunakan untuk mengimport/memasukan method-method dari class/library yang lain, sehingga method tersebut dapat digunakan pada class yang memanggilnya. Fungsi ini harus diletakan pada baris awal program.
salah satu contoh yang sering digunakan yaitu javax.swing (berisi kelas-kelas untuk membentuk aplikasi GUI)
Contoh source code
1. Dialog Box

/**  
  * Write a description of class Dialog1 here.  
  *   
  * @author Nirmala   
  * @version   
  */  
 import javax.swing.JOptionPane;  
 public class Dialog1  
 {  
   public static void main (String[] args)  
   {  
     JOptionPane.showMessageDialog(null,"Welcome to java");  
   }  
 } 

Output:

2. Name Dialog Box

 /**  
  * Write a description of class NameDialog here.  
  *   
  * @author Nirmala  
  * @version (a version number or a date)  
  */  
 import javax.swing.JOptionPane;  
 public class NameDialog  
 {  
   public static void main(String[] args)  
   {  
     String name=JOptionPane.showInputDialog("What is your name?");  
     String message=String.format("Welcome, %s, to Java Programming!", name);  
     JOptionPane.showMessageDialog(null, message);  
   }  
 } 

Output:



3. Memodifikasi Account Test mengguanakan Dialog Box

/**  
  * Write a description of class AccountTestDialogBox here.  
  *   
  * @author Nirmala  
  * @version   
  */  
 import javax.swing.JOptionPane;  
 public class AccountTestDialogBox  
 {  
   public static void main (String[] args)  
   {  
     Account account1 = new Account (50.00);  
     Account account2 = new Account (-7.53);  
     String output1 = String.format ("account1 balance : $%.2f\naccount2 balance : $%.2f\n\n", account1.getBalance(), account2.getBalance());  
     JOptionPane.showMessageDialog (null, output1);  
     String input1 = JOptionPane.showInputDialog ("Enter deposit amount for account1 : ");  
     Double input1a = Double.parseDouble (input1);  
     account1.credit (input1a);   
     String message1 = String.format ("\nadding %s to account1 balance\n\n", input1);  
     JOptionPane.showMessageDialog (null, message1);  
     String output2 = String.format ("account1 balance : $%.2f\naccount2 balance : $%.2f\n\n", account1.getBalance(), account2.getBalance());  
     JOptionPane.showMessageDialog (null, output2);  
     String input2 = JOptionPane.showInputDialog ("Enter deposit amount for account2 : ");  
     Double input2a = Double.parseDouble (input2);  
     account2.credit (input2a);  
     String message2 = String.format ("\nadding %s to account2 balance\n\n", input2);  
     JOptionPane.showMessageDialog (null, message2);  
     String output3 = String.format ("account1 balance : $%.2f\naccount2 balance : $%.2f\n", account1.getBalance(), account2.getBalance());  
     JOptionPane.showMessageDialog (null, output3);  
   }  
 } 

Output:








Semoga bermanfaat :))))). Terimakasih