L03

Due by the end of Tuesday, September 26

Starter Files:

• MoviePrices.java

Today's Activities

• You use if controls when there's something you want to sometimes do and sometimes not do.
• You use if-else controls when you want to do exactly one of two things.
• You use if-else-if controls when you want to do exactly one of three (or more) things. These controls start with an if part, end (usually) with an else part, and have as many else if parts needed to fill out the remaining parts.
• Conditions are always in (parentheses) and only appear after the word if, never after the word else.
• The way we check whether Strings are equal is very different from the way we check if numbers are equal (or different). Check out the GreesieBurger program in the sample code for a reminder of how we check if a word starts with some letters.
• We have exactly one variable for each piece of information. We use that same variable even when the value changes.

On with the activities!

Activity 1: Downloading a Program

Create a new project named L03, with a main program class l03.MoviePrices. Download MoviePrices.java (linked above) into your CSCI1226/L03/src/l03/ folder. Tell your computer that you would like to replace the one that's there.

That program is the sample code version of one we did in class. It reads the user's age and looks up the price they need to pay based on that age. Run the program a few times, trying different ages.

Activity 2: Checking the User's Input

Try running the program with some "stupid" values for the age: negative numbers, and numbers way over 100. Notice that the program doesn't bat an eye (not that it has eyes to bat).

It's generally a good idea to check any number the user enters to make sure that it makes sense. The first change we'd like you to make to the program is to add code to check that the user's age makes sense. If their age is under zero, the program should say "That can't be right!" and ask them to try again:

How old are you? -5 That can't be right! How old are you, really?

The program should read in the age again (using the same variable), then carry on directly into the code for looking up the price:

How old are you, really? 7 Children's price. That'll be $2.99, please.

Activity 3: More Checking

Next, add code to check whether the first age they entered is 100 or more. The program should express surprise, and ask them if they really are that old:

How old are you? 115 Wow, that's surprising! Are you really 115?

The program should read a word as their answer. If their answer starts with "no" (or "NO" or "No" or "nO") then the program should ask them for their actual age:

Are you really 115? No. So what's your real age, then? 15 Youth's price. That'll be $7.99, please.

If their answer is anything else, the program should proceed using the original number they entered:

Are you really 115? Sure am! Senior's price. That'll be $6.99, please.

Activity 4: Yet More Checking the User's Input

In two cases above, we asked the user to re-enter their age, but then we just accepted their second answer without checking it. The user could have re-entered a "stupid" number:

How old are you, really? -700 Children's price. That'll be $2.99, please.

We'd like to add one last check for their age. Just before we get to the part that looks up their price, add a test to see whether their age is less than 0 or more than 120. If it is, then the program should skip announcing the price and instead print the message "I don't believe that you're (whatever age). Please go away."

How old are you, really? -700 I don't believe that you're -700. Please go away.

Of course, if their age is in the valid range, then the normal lookup should proceed:

Are you really 115? Sure am! Senior's price. That'll be $6.99, please.

Once all the activities are completed you can submit your Java program by one of the SUBMIT links above/below.

Make sure you pass in the correct file and that it has the correct name:

• MoviePrices.java

In particular, make sure you submit your modified copy of the .java file. You should find it in your L03/src/l03 folder.

The pass in page will print a little "receipt" for your records. Make sure you read it carefully. Make sure it doesn't have any red text on it at all. Make sure the submitted size is larger than the original size (you should have added quite a bit of code).

Submit this/these files:

• MoviePrices.java

You will be graded on the following:

1. You are identified by both name and A-number as an author of the program,
2. ... in the same way that Mark Young was (and STILL IS)
3. Any age less than zero gets a "not right" message ...
4. ... and gets a new age read in
5. Any age 100 or over gets a "surprising" message ...
6. ... and a request for confirmation
7. ... ... and a new age is read in if (and only if) the user admits the error
8. Any (possibly revised) age under zero gets the "push off" message
9. Any (possibly revised) age over 119 or 120 gets the "push off" message
10. The "push off" message never appears together with an age or price message
11. Initial ages under zero are not tested to see if they are over 100 (proper use of else if)
12. Single condition provided for testing the (possibly revised) age (proper use of && / ||)
13. Code for printing age and price information still in a single block
14. Code is properly indented, uses white space appropriately, and has no overly-long lines