// Fig. 3.13: 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
// Fig. 3.14: 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