Add string challenges

src/SUMMARY.md

@@ -251,13 +251,15 @@
   - [Usage](./enums/usage.md)
   - [Equality](./enums/equality.md)
   - [Comparison to boolean](./enums/comparison_to_boolean.md)
+  - [Challenges](./enums/challenges.md)
 - [Strings II](./strings_ii.md)
   - [lowercase](./strings_ii/lowercase.md)
   - [UPPERCASE](./strings_ii/UPPERCASE.md)
   - [Equality ignoring case](./strings_ii/equality_ignoring_case.md)
   - [Check if empty](./strings_ii/check_if_empty.md)
   - [Check if blank](./strings_ii/check_if_blank.md)
   - [Strip extra whitespace](./strings_ii/strip_extra_whitespace.md)
+  - [Challenges](./strings_ii/challenges.md)
 
 # Control Flow III
 

src/enums/challenges.md

@@ -0,0 +1,107 @@
+# 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 an enum named `Response` which 
+has three variants. `YES`, `NO`, and `MAYBE_SO`.
+
+```java,editable
+// -------------
+// CODE HERE
+// -------------
+
+void main() {
+    System.out.println(
+        Response.YES
+    );
+
+    System.out.println(
+        Response.NO
+    );
+
+    System.out.println(
+        Response.MAYBE_SO
+    );
+}
+```
+
+## Challenge 2.
+
+Write a method named `goodPerformer` which takes 
+in a `String` representing the name of an artist.
+
+If that `String` is equal to `Pitbull` or `Billy Joel`
+return `YES`. If it is equal to `Shaggy` return `NO`.
+Otherwise return `MAYBE_SO`.
+
+Use the enum you defined above.
+
+```java
+// ------------
+// CODE HERE
+// ------------
+
+void main() {
+    Response pitbull = goodPerformer("Pitbull");
+    System.out.println(pitbull);
+
+    Response billyJoel = goodPerformer("Billy Joel");
+    System.out.println(billyJoel);
+
+    Response shaggy = goodPerformer("Shaggy");
+    System.out.println(shaggy);
+
+    Response chappelRoan = goodPerformer("Chappell Roan");
+    System.out.println(chappelRoan);
+}
+```
+
+## Challenge 3.
+
+Make a method named `transition` which takes in a `StopLight`
+and returns the next light it will transition to.
+
+For those who don't drive cars: red lights go to green,
+green lights go to yellow, and yellow lights go to red.
+
+```java,editable
+enum StopLight {
+    RED,
+    YELLOW,
+    GREEN
+}
+
+StopLight transition(StopLight current) {
+    // ------------
+    // CODE HERE
+    // ------------
+}
+
+void main() {
+    var light = StopLight.RED;
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+
+    light = transition(light);
+    System.out.println(light);
+}
+```

src/instance_methods/challenges.md

@@ -116,7 +116,7 @@ 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
+```java,editable
 // ------------
 // CODE HERE
 // ------------
@@ -136,3 +136,71 @@ void main() {
     System.out.println(c);
 }
 ```
+
+## Challenge 5.
+
+Update the definition for the `Taco` class so that it has a method named
+`deluxe`. This should set the taco to have beef, sour cream, cheese,
+and onion. Use the existing instance methods instead of directly accessing
+fields.
+
+```java,editable
+class Taco {
+    boolean beef;
+    boolean sourCream;
+    boolean cheese;
+    boolean onion;
+
+    void addBeef() {
+        this.beef = true;
+    }
+
+    void addSourCream() {
+        this.sourCream = true;
+    }
+
+    void addCheese() {
+        this.cheese = true;
+    }
+
+    void addOnion() {
+        this.onion = true;
+    }
+
+    void deluxe() {
+        // ------------
+        // CODE HERE
+        // ------------
+    }
+}
+
+void main() {
+    var taco = new Taco();
+    taco.deluxe();
+
+    System.out.println("Has Beef: " + taco.beef);
+    System.out.println("Has Sour Cream: " + taco.sourCream);
+    System.out.println("Has Cheese: " + taco.cheese);
+    System.out.println("Has Onion: " + taco.onion);
+}
+```
+
+## Challenge 6.
+
+Why doesn't this code function as you'd expect? Fix it by changing one line.
+
+```java
+class Oscar {
+    boolean grouchy;
+
+    void setGrouchy(boolean grouchy) {
+        grouchy = grouchy;
+    }
+}
+
+void main() {
+    var oscar = new Oscar();
+    oscar.setGrouchy(true);
+    System.out.println(oscar.grouchy);
+}
+```

src/strings_ii/challenges.md

@@ -0,0 +1,113 @@
+# 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.
+
+Write a method named `isUpperCase` which tells you if a
+given `String` is already made of all upper-case characters.
+
+Hint: One way to do this is to call `.toUpperCase` and check
+if the result is the same as the input you were given.
+
+```java,editable
+boolean isUpperCase(String s) {
+    // -----------
+    // CODE HERE
+    // -----------
+}
+
+void main() {
+    // true
+    System.out.println(isUpperCase("ABC"));
+    // false
+    System.out.println(isUpperCase("abc"));
+    // false
+    System.out.println(isUpperCase("AbC"));
+}
+```
+
+## Challenge 2.
+
+Do the same as above, but check if a given `String` is
+made of all lower case letters.
+
+```java,editable
+boolean isLowerCase(String s) {
+    // -----------
+    // CODE HERE
+    // -----------
+}
+
+void main() {
+    // false
+    System.out.println(isLowerCase("ABC"));
+    // true
+    System.out.println(isLowerCase("abc"));
+    // false
+    System.out.println(isLowerCase("AbC"));
+}
+```
+
+## Challenge 3.
+
+Add an instance method named `scream` to the `Muppet` class. This
+should replace the name of the muppet with the name in upper case
+letters + an exclamation point (`!`) at the end.
+
+```java,editable
+class Muppet {
+    String name;
+
+    // -------------
+    // CODE HERE
+    // -------------
+}
+
+void main() {
+    var kermit = new Muppet();
+    kermit.name = "kermit";
+
+    // kermit
+    System.out.println(kermit.name);
+
+    // KERMIT!
+    kermit.scream();
+    System.out.println(kermit.name);
+}
+```
+
+## Challenge 4.
+
+Write a method called `echo`.
+
+If `echo` is given a non-blank `String`, it should print `You Said: <...>` 
+where `<...>` is the `String` they
+gave minus any leading or trailing whitespace.
+
+If `echo` is given a `blank` `String`, it should print `You Didn't Say Anything`.
+
+```java,editable
+void echo(String s) {
+    // -------------
+    // CODE HERE
+    // -------------
+}
+
+void main() {
+    // You Said: Hello
+    echo("Hello");
+
+    // You Said: Hello
+    echo("        Hello         ");
+
+    // You Didn't Say Anything
+    echo("");
+
+    // You Didn't Say Anything
+    echo("                ");
+}
+```