Constructing Objects Lab

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Read the problem Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result. Your tester class should be called BankAccountTester. Use the following class in your solution: [Wplus gives you the BankAccount class code here]

Now You probably feel overwhelmed. You think: What do I do next? You react: Somebody tell me what to do. Professor reaction: take a deep breath, clear your mind and remember…..

….what Eric Berlow said: “Hone in on the sphere of influence that matters most.”

What matters most? There are 2 classes Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result. Your tester class should be called BankAccountTester. Use the following class in your solution: [Wplus gives you the BankAccount class code here]

What matters about the BankAccountTester? You have to write it and BankAccountTester has a main method that constructs a BankAccount and then invokes the methods of the Bank Account and then prints the results. Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result. Your tester class should be called BankAccountTester. Use the following class in your solution: [Wplus gives you the BankAccount class code here]

What matters about the BankAccount class? It is already written for you. You need to understand its structure {You gotta know what is in it.} How do we understand class structures? – Make a UML Class Diagram

Writing a UML Class Diagram to reverse engineer code: Remember the 3 parts of Object Anatomy: name, attributes, methods What is the name of the class?

Name in a Class Diagram

What are the Attributes?

What are the methods

Where is the constructor and are there any overloads?

Where does the constructor go in the class diagram? A constructor is a method that is called when you create a NEW object; the scope is “classifier” instead of “instance”

To add parameters: Click on Properties with the desired constructor highlighted

Go to Parameters and add the name of the parameter, the datatype and kind

Class diagram completed

Remember there are 2 classes The BankAccount and the BankAccountTester

What does the BankAccountTester class look like? What do the words in the problem tell us? “Write a BankAccountTester class whose main method” We know the name of the class and a method name

Now ask yourself… How do these 2 classes interact? What type of diagram will help me understand how they interact? – Sequence Diagram

Put in the object lifelines for each of the objects; there is no instance name for the tester

Why isn't there a instance name for the Tester? Because a tester class is a class with a main method that contains statements to run methods of another class It is the class that makes the calls to the instance of classes [objects] It will occupy space in memory when running but we will not create NEW The main method kicks off the program

Just like a carburetor cant run all by itself and must live in a car to work; a class needs to live in a program Tester class Instance of a class AKA an object

Back to the problem: what is the first thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result.

What is the second thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result.

What is the third thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result.

What is the fourth thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result.

What is the Fifth thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result. Question: is there a dependent operation that must be performed to print the balance? Answer: yes, you have to get the balance before you can print it.

Fifth: Get the balance

And print it

What is the sixth thing the tester does? Write a BankAccountTester class whose main method constructs a bank account, deposits $1,000, withdraws $500, withdraws another $400, and then prints the remaining balance. Also print the expected result.

Now you have a picture of the program and it is time to code.

Launch LabRat and make the file BankAccountTester.java

Construct a new bank account object

Make a deposit [if you don’t remember how to invoke a method go back to object anatomy and look at the method ppt again]

Withdraw

withdraw

Get balance and assign to a variable if you don’t remember how to declare and add value to a variable go back and look at the API lecture

Print balance

Print expected result

Now submit to LabRat and see what happens.