Control Flow

The goal of these exercises is to practise:

• conditional evaluation in Java programs
• use loops to operate on collections we saw earlier in the course

We've provided this starter project, which contains:

• the ControlFlowExercises class with four methods to implement: fizzBuzz, weeksAndDays, and oddAndEvenNumbers

• and a test suite to verify your implementation ControlFlowExercisesTest.

In each method, replace the throw new RuntimeException("Not implemented") with your code.

🐝 FizzBuzz

Implement the fizzBuzz method as described below.

public List<String> fizzBuzz(List<Integer> numbers) {
    // TODO - Implement this method such that 
    //  it creates a list where for each element of the input list ${numbers}
    //  - if the ${element} is divisible by 3, it adds “Fizz” to the list 
    //  - if the ${element} is divisible by 5, it adds “Buzz” to the list 
    //  - if the ${element} is divisible by both 3 and 5, it adds “FizzBuzz” to the list 
    //  - it adds the element to the list in any other case 
    //  - it returns the constructed list
    throw new RuntimeException("Not implemented");
}

Hint

The modulo operator will come in handy in determining whether a number is divisible by another.

📅 Months

Implement the whichMonth method as described below.

public String whichMonth(Integer number) {
    // TODO - Implement this method such that
    //  - it returns the month corresponding to the input ${number}
    //  - if the ${number} is invalid, the method should return "Invalid month number"
    throw new RuntimeException("Not implemented");
}

💯 Collections and Numbers

Exercise 1

Implement the sumOfOddsAndSumOfEvens method as described below.

public Map<String, Integer> sumOfOddsAndSumOfEvens() {
    // TODO - Implement this method such that
    //  - creates and initialises a list of 100 numbers - from 1 to 100
    //  - determines the sum of all the even numbers in the list
    //  - determines the sum of all the odd numbers in the list
    //  - returns a map with two entries:
    //      {"SumOfEvens", calculatedSumOfEvens}, {"SumOfOdds", calculatedSumOfOdds}
    throw new RuntimeException("Not implemented");
}

Exercise 2

Implement the reverse method as described below.

Hint

Use the java.util.Collections class documentation.

public List<Integer> reverse(ArrayList<Integer> numbers) {
    // TODO - Implement this method such that
    //  - it takes an array list of integers
    //  - it returns the list in reverse order
    throw new RuntimeException("Not implemented");
}

✅ Verify Your Implementation

To verify that your code works as expected, run the ControlFlowExercisesTest tests.

In your terminal, ensure that you are in the flow-control folder. Then run the following command in your terminal.

./mvnw clean test

If you are on Windows, run this command instead:

mvnw.cmd clean test

Tests Results

Your implementation is correct when all tests pass:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] ├─ Control Flow Exercises - 0.073s
[INFO] │  ├─ ✔ returns this unit's name - 0.011s
[INFO] │  ├─ ✔ Months[1] 17, Invalid month number - 0.017s
[INFO] │  ├─ ✔ Months[2] 0, Invalid month number - 0.001s
[INFO] │  ├─ ✔ Months[3] 4, April - 0.001s
[INFO] │  ├─ ✔ Months[4] 1, January - 0s
[INFO] │  ├─ ✔ Odd and Even Numbers - 0.001s
[INFO] │  ├─ ✔ Fizz Buzz[1] [1, 2, 4, 7, 8, 11, 13, 17], [1, 2, 4, 7, 8, 11, 13, 17] - 0s
[INFO] │  ├─ ✔ Fizz Buzz[2] [1, 2, 3, 5, 9, 15, 21, 30, 35], [1, 2, Fizz, Buzz, Fizz, FizzBuzz, Fizz, FizzBuzz, Buzz] - 0s
[INFO] │  ├─ ✔ Fizz Buzz[3] [3, 5, 15, 18, 20, 30], [Fizz, Buzz, FizzBuzz, Fizz, Buzz, FizzBuzz] - 0.001s
[INFO] │  ├─ ✔ Fizz Buzz[4] [213, 54, 91, 187, 2001, 2023], [Fizz, Fizz, 91, 187, Fizz, 2023] - 0s
[INFO] │  ├─ ✔ Reverse the list order[1] [1, 2, 4, 7, 8, 11, 13, 17], [17, 13, 11, 8, 7, 4, 2, 1] - 0s
[INFO] │  ├─ ✔ Reverse the list order[2] [1, 2, 3, 5, 9, 15, 21, 30, 35], [35, 30, 21, 15, 9, 5, 3, 2, 1] - 0s
[INFO] │  ├─ ✔ Reverse the list order[3] [123, -5, 0, 1890, 20, 30], [30, 20, 1890, 0, -5, 123] - 0s
[INFO] │  └─ ✔ Reverse the list order[4] [213, 54, 91, 187, 2001, 2023], [2023, 2001, 187, 91, 54, 213] - 0.001s
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 14, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.371 s
[INFO] Finished at: 2023-04-30T00:22:52+01:00
[INFO] ------------------------------------------------------------------------