// Fig. 3.1: GradeBook.java
// Class declaration with one method.

public class GradeBook
{
   // display a welcome message to the GradeBook user
   public void displayMessage()
   {
      System.out.println( "Welcome to the Grade Book!" );
   } // end method displayMessage
} // end class GradeBook

// Fig. 3.2: GradeBookTest.java
// Creating a GradeBook object and calling its displayMessage method.

public class GradeBookTest
{
   // main method begins program execution
   public static void main( String[] args )
   { 
      // create a GradeBook object and assign it to myGradeBook
      GradeBook myGradeBook = new GradeBook(); 

      // call myGradeBook's displayMessage method
      myGradeBook.displayMessage(); 
   } // end main
} // end class GradeBookTest

// Fig. 3.4: GradeBook.java
// Class declaration with a method that has a parameter.

public class GradeBook
{
   // display a welcome message to the GradeBook user
   public void displayMessage( String courseName )
   {
      System.out.printf( "Welcome to the grade book for\n%s!\n", 
         courseName );
   } // end method displayMessage
} // end class GradeBook

// Fig. 3.5: GradeBookTest.java
// Create GradeBook object and pass a String to 
// its displayMessage method.
import java.util.Scanner; // program uses Scanner

public class GradeBookTest
{
   // main method begins program execution
   public static void main( String[] args )
   { 
      // create Scanner to obtain input from command window
      Scanner input = new Scanner( System.in );

      // create a GradeBook object and assign it to myGradeBook
      GradeBook myGradeBook = new GradeBook(); 

      // prompt for and input course name
      System.out.println( "Please enter the course name:" );
      String courseName = input.nextLine(); // read a line of text
      System.out.println(); // outputs a blank line

      // call myGradeBook's displayMessage method 
      // and pass courseName as an argument
      myGradeBook.displayMessage( courseName );
   } // end main
} // end class GradeBookTest

// Fig. 3.7: GradeBook.java
// GradeBook class that contains a courseName instance variable 
// and methods to set and get its value.

public class GradeBook
{
   private String courseName; // course name for this GradeBook

   // method to set the course name
   public void setCourseName( String name )
   {
      courseName = name; // store the course name
   } // end method setCourseName

   // method to retrieve the course name
   public String getCourseName()
   {
      return courseName;
   } // end method getCourseName

   // display a welcome message to the GradeBook user
   public void displayMessage()
   {
      // calls getCourseName to get the name of 
      // the course this GradeBook represents
      System.out.printf( "Welcome to the grade book for\n%s!\n", 
         getCourseName() );
   } // end method displayMessage
} // end class GradeBook

// Fig. 3.8: GradeBookTest.java
// Creating and manipulating a GradeBook object.
import java.util.Scanner; // program uses Scanner

public class GradeBookTest
{
   // main method begins program execution
   public static void main( String[] args )
   { 
      // create Scanner to obtain input from command window
      Scanner input = new Scanner( System.in );

      // create a GradeBook object and assign it to myGradeBook
      GradeBook myGradeBook = new GradeBook(); 

      // display initial value of courseName
      System.out.printf( "Initial course name is: %s\n\n",
         myGradeBook.getCourseName() );

      // prompt for and read course name
      System.out.println( "Please enter the course name:" );
      String theName = input.nextLine(); // read a line of text
      myGradeBook.setCourseName( theName ); // set the course name
      System.out.println(); // outputs a blank line

      // display welcome message after specifying course name
      myGradeBook.displayMessage();
   } // end main
} // end class GradeBookTest

// Fig. 3.10: GradeBook.java
// GradeBook class with a constructor to initialize the course name.

public class GradeBook
{
   private String courseName; // course name for this GradeBook

   // constructor initializes courseName with String argument
   public GradeBook( String name )
   {
      courseName = name; // initializes courseName
   } // end constructor

   // method to set the course name
   public void setCourseName( String name )
   {
      courseName = name; // store the course name
   } // end method setCourseName

   // method to retrieve the course name
   public String getCourseName()
   {
      return courseName;
   } // end method getCourseName

   // display a welcome message to the GradeBook user
   public void displayMessage()
   {
      // this statement calls getCourseName to get the 
      // name of the course this GradeBook represents
      System.out.printf( "Welcome to the grade book for\n%s!\n", 
         getCourseName() );
   } // end method displayMessage
} // end class GradeBook

// Fig. 3.11: GradeBookTest.java
// GradeBook constructor used to specify the course name at the 
// time each GradeBook object is created.

public class GradeBookTest
{
   // main method begins program execution
   public static void main( String[] args )
   { 
      // create GradeBook object
      GradeBook gradeBook1 = new GradeBook( 
         "CS101 Introduction to Java Programming" ); 
      GradeBook gradeBook2 = new GradeBook( 
         "CS102 Data Structures in Java" );
      
      // display initial value of courseName for each GradeBook
      System.out.printf( "gradeBook1 course name is: %s\n",
         gradeBook1.getCourseName() );
      System.out.printf( "gradeBook2 course name is: %s\n",
         gradeBook2.getCourseName() );
   } // end main
} // end class GradeBookTest

// 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

// Fig. 3.17: Dialog1.java
// Printing multiple lines in dialog box.
import javax.swing.JOptionPane; // import class JOptionPane

public class Dialog1
{
   public static void main( String[] args )
   {
      // display a dialog with a message 
      JOptionPane.showMessageDialog( null, "Welcome\nto\nJava" );
   } // end main
} // end class Dialog1

// Fig. 3.18: NameDialog.java
// Basic input with a dialog box.
import javax.swing.JOptionPane;

public class NameDialog
{
   public static void main( String[] args )
   {
      // prompt user to enter name
      String name =                                          
         JOptionPane.showInputDialog( "What is your name?" );
      
      // create the message
      String message =                                              
         String.format( "Welcome, %s, to Java Programming!", name );

      // display the message to welcome the user by name 
      JOptionPane.showMessageDialog( null, message );
   } // end main
} // end class NameDialog