Take-home Assessment A4: Budgeter

Due July 20, 2021 11:59:59 pm PDT

This assessment will assess your mastery of the following objectives:

Write a functionally correct Java program to produce specified console output.
Write conditional (if) statements to conditionally execute code.
Write and call methods that accept parameters and return values to manage information flow.
Use Scanner to accept and process user input.
Follow prescribed conventions for spacing, indentation, naming methods, and header comments.

Program Behavior

This program prompts a person for income and expense amounts, then calculates their net monthly income. Unlike previous assessments, this program's behavior is dependent on input from a user (user input is bold and underlined in the examples to the left and on the next page). Your output should match our examples exactly when given the same input, but if the input changes, the output will also. Additional execution logs will be posted on the course website, and you can use the Mark button in Ed to check your output for various inputs.

Expected Output: User input is bold and underlined in the sample output in this document

This program asks for your monthly income and
expenses, then tells you your net monthly income.

How many categories of income? 3
    Next income amount? $1000
    Next income amount? $250.25
    Next income amount? $175.50

Enter 1) monthly or 2) daily expenses? 1
How many categories of expense? 4
    Next expense amount? $850
    Next expense amount? $49.95
    Next expense amount? $75
    Next expense amount? $120.67

Total income = $1425.75 ($45.99/day)
Total expenses = $1095.62 ($35.34/day)

You earned $330.13 more than you spent this month.
You're a big saver.
<< Your custom message goes here >>

This program asks for your monthly income and
expenses, then tells you your net monthly income.

How many categories of income? 2
    Next income amount? $800
    Next income amount? $201.30

Enter 1) monthly or 2) daily expenses? 2
How many categories of expense? 1
    Next expense amount? $45.33

Total income = $1001.3 ($32.3/day)
Total expenses = $1405.23 ($45.33/day)

You spent $403.93 more than you earned this month.
You're a big spender.
<< Your custom message goes here >>

Make sure that the format and structure of your output exactly match the given logs.

The program begins with an introductory message that briefly explains the program, then prompts the user for the number of income categories and reads in that many income amounts. Next, the program asks whether the user would like to enter monthly or daily expenses. (The user enters 1 for monthly and 2 for daily.) When entering monthly expenses, the amounts input are the total amount for the month. When entering daily expenses, the amounts input are for a single day, and should be multiplied by the number of days in a month to get the monthly total (see below). The program will then read in a number of expense categories and an amount for each category, similar to how income was read.

After reading all the user input, the program should then print out the total amount of income and expenses for the month, as well as the average income and expense per day. You may assume a month has exactly 31 days, though you should use a class constant so that your program can be easily modified to change this assumption (see below). The program should print out whether the user spent or earned more money for the given month and by how much. If income and expenses were exactly equal, the user is considered to have spent $0 more than they earned (as opposed to earning $0 more than they spent).

Finally, the program should print out which category the user falls into based on their net income for the month, where the net income is the result of subtracting the user's expenses from their income. The category should be followed by a custom message of your choice about the user's spending habits. This message must be different for each of the four ranges shown below, and should consist of one line of any non-offensive text you choose.

Each category must have a separate, unique message.

The categories are defined below. You may find this graphic (seen below) helpful in understanding the boundaries of the various categories.

Net income range	Category
More than +$250	big saver
More than $0 but not more than than +$250	saver
More than -$250 but not more than $0	spender
-$250 or less	big spender

Income Categories Visualisation

All monetary values in output should be rounded to two decimal places using a rounding method (as shown in lecture). If the second digit after the decimal point (the "hundreths" digit) is a zero, your program should not print out this zero. (e.g. your program will print $3.5 instead of $3.50) This is acceptable and expected, and you should NOT attempt to fix this. However, you MUST print out two digits if the second digit is not a zero.

In particular, you MAY NOT use the printf method on this assessment.

Development Strategy

As usual, we recommend you approach the program in stages, rather than trying to complete everything at once. Specifically, we suggest implementing functionality in the following order:

Income: Prompt for income categories and amounts and compute and print the total monthly income.
Monthly expenses: Prompt for monthly expense categories and amounts (as if the user had entered 1 when asked for monthly or daily expenses) and compute and print the total monthly expenses.
Daily expenses: Prompt the user to choose monthly or daily expenses, then compute and print total expenses based on the choice.
Averages: Compute and print daily average income and expenses.
Net income: Compute and print net income and spender/saver category.

Hints

This assessment is significantly more complex than previous ones. The following suggestions and hints may help you be more successful:

Approach the program one part at a time, rather than trying to write most or all of the program at once. Add additional output to test incomplete portions of your code, and compile and test often.
Remember to remove any debugging output before submitting
You will need to use a cumulative sum to compute the total income and expenses, as described in lecture and section 4.2 of the textbook.
Be careful of using integer division when you should be using real number division, and vice versa. Values of type int can be used when a double is expected, but to use a double where you need an int you will need to use a cast, such as:
double d = 5.678;
int i = (int)d; // i = 5
If you are receiving "Cannot find symbol" errors from the compiler, look carefully at your parameters and return values and ensure they are all included and named correctly
Remember that, in most cases, you will need to store the value returned from a method in a variable.

Implementation Guidelines

User Input

This program requires you to process user input, which you must do using a Scanner. You may assume that all monetary inputs will be real numbers, and that all other input will be integers. You may also assume the user always enters valid input. Specifically, you may assume that:

the user will always enter a value of the correct type
the user will always enter a number of income and expense categories ≥ 1
the user will only ever enter 1 or 2 when asked whether to enter monthly or daily expenses
the user will only enter a non-negative amount for each category of income and expense

Class Constant

As described above, your program should assume there are 31 days in a month by default, but this value should be able to be easily changed. You must introduce a class constant for the number of days in a month, and use this constant throughout your program. See the list of files below for example logs with alternate values for the constant. The Mark button in Ed will test your program with different constant values. To ensure our testing and grading scripts work correctly, you must name your constant DAYS_IN_MONTH. In addition, please set the value of the constant to 31 before submitting your work.

Make sure you declare your constant exactly right, using the keywords public static final, in that order.

Working with Numbers/Rounding

For all numerical values in your program, you should use the type (int or double) that is more appropriate for the value. In particular, you should NOT simply use double for all values. In addition, you must not round values until they are output; all calculations should be performed using the full values.

Working with Strings

There may be places in this assessment where you want to work with Strings. Strings are an Object in Java, which means that comparing them using == doesn't work correctly. To compare Strings you must use the .equals() method.

Permitted Java Features

For this assessment, you are restricted to Java concepts covered in chapters 1 through 4 of the textbook. In particular, you MUST use parameters and return values. You are NOT permitted to use the printf method or arrays on this assessment.

Code Quality Guidelines

In addition to producing the desired behavior, your code should be well-written and meet all expectations described in the general rubric and the Code Quality Guide. For this assessment, pay particular attention to the following elements:

Capturing Structure

You should attempt to eliminate all redundancy in your program, and your main method should be a concise summary of your program's structure. You should not produce any output in your main method, though you may have more code in main than you have on previous assessments. In addition, each method should perform a single, coherent task. To receive the highest grades, your program must include at least four (4) non-trivial methods other than main. (For reference, our solution consists of 86 lines of code, 58 of which are "substantive", and 7 methods besides main.)

Your program must include at least four nontrivial methods, but you are NOT expected to match our line or method count.

Using Parameters and Returns

Your program should utilize parameters and return values effectively to produce a well-structured program as described above. Your methods should not accept any unnecessary parameters. For this assessment, a parameter is considered unncessary if its value is unused, is always the same as the value as another parameter, or can be directly computed from the values of other parameters. In particular, your program should include only a single Scanner which is passed as a parameter to all required methods. You should NOT declare your Scanner as a constant; you must pass it as a parameter. Your program should also utilize return values to avoid "chaining" (where each method calls the next without returning to main).

The case study in chapter 4 of the textbook and the election program from lecture both demonstrate how to avoid chaining.

Using Conditionals

Your program will need to utilize conditionals (if statements) at various points to achieve the correct behavior. You are expected to use the most appropriate form of these statements (if, if-else, and/or if-else if) for each situation and to factor common code out of each branch.

Code Aesthetics

Your code should be properly indented, make good use of blank lines and other whitespace, and include no lines longer than 100 characters. Your class, methods, variables, and constant should all have meaningful and descriptive names and follow the standard Java naming conventions. (e.g. ClassName, methodOrVariableName, CONSTANT_NAME) See the Code Quality Guide for more information.

Commenting

Your code should include a header comment at the start of your program, following the same format described in previous assessments. Your code should also include a comment at the beginning of each method that describes that methods behavior. Method comments should also explicitly name and describe all parameters to that method and describe the method's return value (if it has one). Comments should be written in your own words (i.e. not copied and pasted from this spec) and should not include implementation details (such as describing loops or expressions included in the code). See the Code Quality Guide for examples and more information.

Running and Submitting

You should write your program in a file named Budgeter.java and submit it in Ed. You can run your program by clicking the "Run" button in Ed. This will compile and execute your code and show you any errors, or the output of your program if it runs correctly. If you believe your output is correct, you can submit your work by clicking the "Mark" button in the Ed assessment. You will see the results of some automated tests. These tests are not fully indicative of the grade you will receive on this assessment, and your grade on this assessment is not final until you have received feedback from your TA.

You may submit your work as often as you like until the deadline; we will always grade your most recent submission before the deadline. Note the due date and time carefully -- work submitted after the due time will not be accepted.

Getting Help

If you find you are struggling with this assessment, make use of all the course resources that are available to you, such as:

Reviewing relevant examples from lectures, section, and lab
Reading the textbook
Visiting support hours
Posting a question on the message board

Collaboration Policy

Reflection

In addition to your code, you must submit answers to short reflection questions. These questions will help you think about what you learned, what you struggled with, and how you can improve next time. The questions are in the Reflection slide in the Ed assessment.