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Exercise 1: Pet

Your goal is to write a class named Pet, which allows us to store information about our pets.

The Pet class should have the following methods:

• Pet(name, age, kind) constructor: takes name (a string), age (an integer, in years), and kind (a string, like "dog" or "cat"), with all three as instance variables
• rename(name): updates the name of a pet; returns nothing
• updateAge(): updates the age when the pet has a birthday; returns nothing

Create a file Pet.kt and put your code there. To get you started, here is a main function you can use to test part of your implementation:

fun main() {
    // Make a few Pet objects
    val lulu: Pet = Pet("Lulu", 13, "cat")
    val hobbes: Pet = Pet("Hobbes", 12, "cat")
    val cheddar: Pet = Pet("Cheddar", 1, "dog")
    val mal: Pet = Pet("Marshmallow", 1, "dog")

    // Print some info
    println("Hobbes is currently ${hobbes.age} years old, and Lulu is ${lulu.age}.")
    
    print("The dogs are: ")
    for (pet: Pet in listOf(lulu, hobbes, cheddar, mal)) {
        if (pet.kind == "dog") {
            print("${pet.name} ")
        }
    }
    println()

    // Hobbes has a birthday next Tuesday!
    hobbes.updateAge()
    println("On Tuesday Hobbes will be older!  (${hobbes.age} years)")
}

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Exercise 2: MyMap

If you finished Exercise 1 early, you can start Exercise 2 for fun. We won’t go over it in class.

Your goal is to write a class named MyMap, which allows us to associate keys with values. For example, we may want to map the string "blue" to the number 3 and the string "yellow" to the number 4.

The MyMap class should have the following methods:

• MyMap() constructor: takes no actual parameters, but initializes necessary data structures; returns None
• add(key, value): adds a new mapping from key (assume it’s a String) to value (assume it’s an Int), or updates the mapping if key is already present; returns None
• get(key): looks up the value mapped to by key; returns the value for key or None if no mapping exists for key
• getSize(): calculates the number of key-value pairs; returns that number (an int)

Think carefully about what you need to store to be able to handle any number of key-value pairs.

You should create a new file named Map.kt and put your class definition there. It should start like this:

class MyMap {
    // TODO: initiailize any necessary data structures

    // TODO: add methods
}

Here’s a simple main function you can use to try some of the MyMap functions out:

fun main() {
    val map: MyMap = MyMap()

    map.add("blue", 314)
    map.add("yellow", 271)

    println("There are ${map.getSize()} pairs in the map.")
}

How would you write code to test the rest of the class definition?

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