Account - Java Sample Program

// Account.java
// Account class with a constructor to validate and 
// initialize instance variable balance of type double.

public class Account
{   
   private double balance; // instance variable that stores the balance

   // constructor  
   public Account( double initialBalance )
   {
      // validate that initialBalance is greater than 0.0; 
      // if it is not, balance is initialized to the default value 0.0
      if ( initialBalance > 0.0 ) 
         balance = initialBalance; 
   } // end Account constructor

   // credit (add) an amount to the account
   public void credit( double amount )
   {      
      balance = balance + amount; // add amount to balance 
   } // end method credit

   // return the account balance
   public double getBalance()
   {
      return balance; // gives the value of balance to the calling method
   } // end method getBalance
} // end class Account

// AccountTest.java

// Inputting and outputting floating-point numbers with Account objects.

import java.util.Scanner;

public class AccountTest

{

   // main method begins execution of Java application

   public static void main( String[] args ) 

   {

      Account account1 = new Account( 50.00 ); // create Account object

      Account account2 = new Account( -7.53 ); // create Account object

      // display initial balance of each object

      System.out.printf( "account1 balance: $%.2f\n", 

         account1.getBalance() );

      System.out.printf( "account2 balance: $%.2f\n\n", 

         account2.getBalance() );

      

      // create Scanner to obtain input from command window

      Scanner input = new Scanner( System.in );

      double depositAmount; // deposit amount read from user

      System.out.println( "Enter deposit amount for account1: " ); // prompt

      depositAmount = input.nextDouble(); // obtain user input

      System.out.printf( "\nadding %.2f to account1 balance\n\n", 

         depositAmount );

      account1.credit( depositAmount ); // add to account1 balance

      // display balances

      System.out.printf( "account1 balance: $%.2f\n", 

         account1.getBalance() );

      System.out.printf( "account2 balance: $%.2f\n\n", 

         account2.getBalance() );

      System.out.print( "Enter deposit amount for account2: " ); // prompt

      depositAmount = input.nextDouble(); // obtain user input

      System.out.printf( "\nadding %.2f to account2 balance\n\n", 

         depositAmount );

      account2.credit( depositAmount ); // add to account2 balance

      // display balances

      System.out.printf( "account1 balance: $%.2f\n", 

         account1.getBalance() );

      System.out.printf( "account2 balance: $%.2f\n", 

         account2.getBalance() );

   } // end main

} // end class AccountTest