// file GreeterTest2.java

// CH's version 2 of the Greeter class adds an "instance variable" called "name"
// which stores a reference to a String object, and a class constructor. Also
// introduces the concept of method parameters and arguments

// -> The instance var's of a class store the "state" of its objects (i.e. what 
//    each object "knows").

// -> The constructor is called automatically whenever an object is created 
//    ("instantiated") via the "new" operator.
//
// -> The purpose of a constructor is to set the state of the object being
//    constructed, by initializing its instance var's

// Note that the Greeter constructor has a String "parameter variable" (i.e., 
// you must supply a String argument when creating a Greeter object.

/**
 * Improved version of Greeter class allows user to "customize" the message
 * to be printed.
 */
class Greeter
{
   private String name ;			// note instance variable
   
   /**
    * Create a Greeter object with name supplied by user
    */
   public Greeter(String aName)		// constructor with String parameter var
   {
      name = aName ;				// initializing the instance var to the
   }								// value of the parameter

   /**
    * Print a personalized greeting
    */
   public String sayHello()
   {
      String message = "Hello, " + name + "!" ;
      return message;
   }

}

/**
 * A test class for the Greeter class
 */
public class GreeterTest2
{
   public static void main(String[] args)
   {
      Greeter worldGreeter = new Greeter("World") ;
      System.out.println(worldGreeter.sayHello()) ;

      Greeter dollyGreeter = new Greeter("Dolly") ;
      System.out.println(dollyGreeter.sayHello()) ;
   }
}

/* program output

Hello, World!
Hello, Dolly!

*/