Add challenges for instance methods

src/instance_methods/challenges.md

@@ -1 +1,138 @@
 # Challenges
+
+Remember the rules for this are
+
+- 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.
+
+Make a class named `PirateShip` which has one `int` field
+named `crewSize`.
+
+Add an instance method to that class named `sail` which outputs
+
+```
+N sailors, ready to sail!
+```
+
+Where *N* is the size of the crew.
+
+```java,editable
+// ----------------
+// CODE HERE
+// ----------------
+
+void main() {
+    PirateShip ship = new PirateShip();
+    ship.crewSize = 25;
+    ship.sail();
+}
+```
+
+## Challenge 2.
+
+Make a class named `StringArrayView` which has
+one `String[]` field named `value`
+ and two methods named `get` and `length`.
+
+`get` should take in an index and return the matching element
+of the array.
+
+`length` should take no arguments and give the length of the array.
+
+```java,editable
+// ----------------
+// CODE HERE
+// ----------------
+
+void main() {
+    StringArrayView view = new StringArrayView();
+    view.value = new String[] { "A", "B", "C" };
+
+    // 3
+    System.out.println(view.length());
+
+    // A
+    System.out.println(view.get(0));
+
+    // C
+    System.out.println(view.get(2));
+}
+```
+
+## Challenge 3.
+
+Alter the `VoiceActor` class so that it has a method named `fullName`
+that returns their `firstName` followed by their `lastName` and separated
+by a space.
+
+If their `lastName` is `null`, you should have no trailing space.
+If their `firstName` is `null`, you should have no leading space.
+
+If both their `firstName` and `lastName` are `null`, you should
+return `"No Name"`.
+
+```java,editable
+class VoiceActor {
+    String firstName;
+    String lastName;
+
+    // -----------------
+    // CODE HERE
+    // -----------------
+}
+
+void main() {
+    VoiceActor goku = new VoiceActor();
+    goku.firstName = "Masako";
+    goku.lastName = "Nozawa";
+
+    // "Masako Nozawa"
+    String gokuFullName = goku.fullName();
+    System.out.println(gokuFullName);
+
+    // "Nozawa"
+    goku.firstName = null;
+    gokuFullName = goku.fullName();
+    System.out.println(gokuFullName);
+
+    // "No Name"
+    goku.lastName = null;
+    gokuFullName = goku.fullName();
+    System.out.println(gokuFullName);
+
+    // "Horikawa"
+    Person vegeta = new VoiceActor();
+    vegeta.lastName = "Horikawa";
+    System.out.println(vegeta.fullName());
+}
+```
+
+## Challenge 4.
+
+Make a `Rectange` class which has a `width` field and a `height`
+field. Give it an instance method named `toCharArray` which gives
+a `char[]` that can be printed to display a rectangle of the given
+width and height.
+
+```java
+// ------------
+// CODE HERE
+// ------------
+
+void main() {
+    Rectangle rectangle = new Rectangle();
+    rectangle.width = 3;
+    rectangle.height = 4;
+
+    /*
+        ***
+        ***
+        ***
+        ***
+    */
+    char[] c = rectangle.toCharArray();
+    System.out.println(c);
+}
+```