1. You can work in groups on this program.
Java
12/10/2015
Objects

2. Demonstrate Chatbots
Chatbot 2-3: Cat/Dog/Teacher/Blank/+ 3 Responses, + 3 Keywords
Chatbot 4: I want…/ I like…
Chatbot 5: Response Array / + 4 more random responses

3. Learning Objectives
Be able to read a program that uses objects, classes and methods.
Be able to develop and test a class from scratch.

4. public class Account {
private double balance;
public Account( double initialBalance )
if ( initialBalance > 0.0 )
balance = initialBalance; }
public void credit( double amount )
balance = balance + amount; // add amount to balance
public double getBalance()
return balance;
Find the …
Class name
Constructor
Methods
Instance Variable
What does the constructor do?

5. // Fig. 3.14: AccountTest.java
// Create and manipulate an Account object.
import java.util.Scanner;
public class AccountTest {
public static void main( String args[] )
Account account1 = new Account( );
Account account2 = new Account( );
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;
depositAmount = input.nextDouble();
System.out.printf( "\nadding %.2f to account1 balance\n\n", depositAmount );
account1.credit( depositAmount );
System.out.print( "Enter deposit amount for account1: " );
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: " );
depositAmount = input.nextDouble();
System.out.printf( "\nadding %.2f to account2 balance\n\n", depositAmount );
account2.credit( depositAmount );
System.out.printf( "account2 balance: $%.2f\n",
account2.getBalance() );
} // end main
} // end class AccountTest
Dry run the above code using the following values for input: 25.53,

6. Checking the Dry Run account1 balance: $50.00 account2 balance: $0.00
Enter deposit amount for account1: 25.53
Adding to account1 balance
account1 balance: $75.53
Enter deposit for account2:
Adding to account2 balance
account2 balance: $123.45

7. Making a Class from Scratch
We will develop a class representing Fractions.

8. Going from idea to code: Fractions
What attributes does a fraction have. Data, information, variables, …
Numerator
Denominator
How should the fraction be created? Constructors
Given a numerator and denominator
A default value if nothing is given.
What behaviors does a fraction have? Verbs, operations, functions, methods.
Public
+, -, *, /
Private
Reduce
Find the greatest common factor to help reducing.

9. For starters Write the fraction class Create constructors
Sample call statement
Fraction fraction = new Fraction(25, 30);
Fraction fraction2 = new Fraction();
Show fraction
Multiply fractions
Write the code for the constructors. We’ll go over it in class in a bit.

10. Now add the following methods.
toString()
Will return a String representation of the Fraction
For example if the numerator = 5 and the denominator = 6 it will return “5/6”
Sample call statement from the main body
System.out.println(fractionObject.toString();
mult
To multiply one fraction by another.
Sample call statement.
fractionObject1.mult(fractionObject2);

11. Sample FractionTest program
//FractionTest.java
//This program is to check the Fraction class
public class FractionTest {
public static void main(String args[] )
Fraction fraction = new Fraction(25, 30);
System.out.println(fraction.toString());
Fraction fraction2 = new Fraction(3,4);
fraction2=fraction.mult(fraction2); }

12. For today Add the following methods to the fraction class. Pushes
toString()
divide
Add (Include creating common denominators)
Pushes
subtract
Reduce
Test it using the Object Bench in BlueJ or by using a driver class.