constructors challenges

Author: bowbahdoe

src/SUMMARY.md

@@ -290,6 +290,7 @@
   - [Invariants](./constructors/invariants.md)
   - [Overloads](./constructors/overloads.md)
   - [Delegation](./constructors/delegation.md)
+  - [Challenges](./constructors/challenges.md)
 - [Global Fields](./global_fields.md)
   - [Default Values](./global_fields/default_values.md)
   - [Final Fields](./global_fields/final_fields.md)

src/constructors/challenges.md

@@ -0,0 +1,147 @@
+# Challenges
+
+- Try to use only the information given up to this point in this book.
+- Try not to give up until you've given it a solid attempt
+
+## Challenge 1.
+
+Write a `Shoe` class. Give each shoe a `name` field and a `quality` field.
+Have these fields be initialized inside of a constructor.
+
+```java,editable
+enum Quality {
+    SUPA_FINE,
+    FINE,
+    SUB_FINE
+}
+
+// CODE HERE
+
+void main() {
+    Shoe nike = new Shoe("Nikes", Quality.SUB_FINE);
+    System.out.println(
+        "SHOE: " + nike.name + ", " + nike.quality
+    );
+
+
+    Shoe moccasin = new Shoe("Moccasins", Quality.SUPA_FINE);
+    System.out.println(
+        "SHOE: " + moccasin.name + ", " + moccasin.quality
+    );
+}
+```
+
+## Challenge 2.
+
+Add a new `price` field to the `Shoe` class you wrote above.
+
+Add a new constructor which accepts a third argument to set the `price`.
+Keep the old two argument constructor around as well. When that one is
+used set `price` to `null`.
+
+Hint: Use `Double` to represent a nullable price.
+
+```java,editable
+enum Quality {
+    SUPA_FINE,
+    FINE,
+    SUB_FINE
+}
+
+// CODE HERE
+
+void main() {
+    Shoe jays = new Shoe("Air Jordans", Quality.FINE, 130.0);
+    System.out.println(
+        "SHOE: " + jays.name + ", " + jays.quality + ", $" + jays.price
+    );
+
+    Shoe nike = new Shoe("Nikes", Quality.SUB_FINE, 25);
+    System.out.println(
+        "SHOE: " + nike.name + ", " + nike.quality + ", $" + jays.price
+    );
+
+
+    Shoe moccasin = new Shoe("Moccasins", Quality.SUPA_FINE);
+    System.out.println(
+        "SHOE: " + moccasin.name + ", " + moccasin.quality + ", $" + jays.price
+    );
+}
+```
+
+## Challenge 3.
+
+Alter the `Shoe` class so that the `price` field is final.
+Alter its constructors so that if they are given a negative
+value they throw an exception instead of finishing normally.
+
+Keep in mind that while `null` is allowed (you might not know the price)
+a negative number wouldn't be. Nobody is paying you to take their shoes.[^holes]
+
+```java,editable
+enum Quality {
+    SUPA_FINE,
+    FINE,
+    SUB_FINE
+}
+
+// CODE HERE
+
+void main() {
+    Shoe jays = new Shoe("Air Jordans", Quality.FINE, 130.0);
+    System.out.println(
+        "SHOE: " + jays.name + ", " + jays.quality + ", $" + jays.price
+    );
+
+    Shoe nike = new Shoe("Nikes", Quality.SUB_FINE, 25);
+    System.out.println(
+        "SHOE: " + nike.name + ", " + nike.quality + ", $" + jays.price
+    );
+
+
+    Shoe moccasin = new Shoe("Moccasins", Quality.SUPA_FINE);
+    System.out.println(
+        "SHOE: " + moccasin.name + ", " + moccasin.quality + ", $" + jays.price
+    );
+
+    Shoe shouldCrash = new Shoe("Base Ball Cleats", Quality.SUPA_FINE, -10);
+}
+```
+
+[^holes]: If they do, you are going to dig holes in the desert in search of treasure that rightfully belongs
+to you.
+
+## Challenge 4.
+
+If you haven't yet, rewrite your `Shoe` constructors so only one of them actually sets fields
+and the other just delegates to that one.
+
+```java,editable
+enum Quality {
+    SUPA_FINE,
+    FINE,
+    SUB_FINE
+}
+
+// CODE HERE
+
+void main() {
+    Shoe jays = new Shoe("Air Jordans", Quality.FINE, 130.0);
+    System.out.println(
+        "SHOE: " + jays.name + ", " + jays.quality + ", $" + jays.price
+    );
+
+    Shoe nike = new Shoe("Nikes", Quality.SUB_FINE, 25);
+    System.out.println(
+        "SHOE: " + nike.name + ", " + nike.quality + ", $" + jays.price
+    );
+
+
+    Shoe moccasin = new Shoe("Moccasins", Quality.SUPA_FINE);
+    System.out.println(
+        "SHOE: " + moccasin.name + ", " + moccasin.quality + ", $" + jays.price
+    );
+
+    Shoe shouldCrash = new Shoe("Base Ball Cleats", Quality.SUPA_FINE, -10);
+}
+```