Write more of the classes section

book.toml

@@ -16,16 +16,6 @@ additional-js = ["ferris.js"]
 enable = true # whether or not to enable section folding
 level = 0     # the depth to start folding
 
-[preprocessor.features]
-command = "python3 features.py"
-# Going to start writing the rest of the book
-# Assuming this is true
-toplevel_anonymous_class = true
-# Not ready
-simple_io = false
-# Turn on when Java 21 released
-java_21 = false
-
 [output.html.playground]
 editable = true
 

src/SUMMARY.md

@@ -180,26 +180,23 @@
   - [Inferred Types](./arguments/inferred_types.md)
   - [Challenges](./arguments/challenges.md)
 
-- [Return](./return_values.md)
-  - [Return Values](./return_values/return_values.md)
-  - [Conversion](./return_values/conversion.md)
+- [Return Values](./return_values.md)
+  - [Declaration](./return_values/declaration.md)
+  - [Return Statement](./return_values/return_statement.md)
+  - [Exhaustiveness](./return_values/exhaustiveness.md)
   - [void](./return_values/void.md)
+  - [Return in void methods](./return_values/return_in_void_methods.md)
+  - [Conversion](./return_values/conversion.md)
   - [Unreachable Statements](./return_values/unreachable_statements.md)
-  - [Pure Functions](./return_values/pure_functions.md)
-  - [Impure Functions](./return_values/impure_functions.md)
 
 # Data Types III
 
-- [Identity Types](./identity_types.md)
-  - [Comparison with ==](./identity_types/comparison_with_equalsequals.md)
-- [Primitive Types](./primitive_types.md)
 - [null](./null.md)
   - [Null as Absence](./null/null_as_absence.md)
+  - [Null as Unknown](./null/null_as_unknown.md)
   - [Checking for null](./null/checking_for_null.md)
-  - [Field Access](./null/field_access.md)
-  - [Instance Methods](./null/instance_methods.md)
+  - [NullPointerException](./null/null_pointer_exception.md)
 - [Boxed Primitives](./boxed_primitives.md)
-  - [Primitive Types](./boxed_primitives/primitive_types.md)
   - [Integer](./boxed_primitives/integer.md)
   - [Double](./boxed_primitives/double.md)
   - [Character](./boxed_primitives/character.md)
@@ -209,38 +206,48 @@
   - [Arrays of Boxed Primitives](./boxed_primitives/arrays_of_boxed_primitives.md)
   - [Challenges](./boxed_primitives/challenges.md)
 - [Arrays II](./arrays_ii.md)
+  - [Initializion with Size](./arrays_ii/initialization_with_size.md)
   - [Default Values](./arrays_ii/default_values.md)
-  - [Populate Array]()
+  - [Populate Arrays](./arrays_ii/populate_arrays.md)
 
 # Code Structure II
 
 - [Classes](./classes.md)
-
+  - [The meaning of the word Class](./classes/the_meaning_of_the_word_class.md)
   - [Class Declaration](./classes/class_declaration.md)
-  - [User Defined Types](./classes/user_defined_types.md)
   - [Naming Classes](./classes/naming_classes.md)
-  - [Field Declaration](./classes/field_declaration.md)
-  - [Field Access](./classes/field_access)
-  - [Naming Fields](./classes/naming_fields.md)
-  - [new](./classes/new.md)
-  - [Zero Values](./classes/zero_values.md)
+  - [Instances](./classes/instances.md)
+  - [Fields](./classes/fields.md)
+  - [Field Initialization](./classes/field_initialization.md)
+  - [Field Access](./classes/field_access.md)
+  - [Field Default Values](./classes/field_default_values.md)
   - [Aliasing](./classes/aliasing.md)
-  - [null](./classes/null.md)
+  - [Return Multiple Values](./classes/return_multiple_values.md)
 
-- [Constructors](./constructors.md)
+- [Instance Methods](./instance_methods.md)
+  - [Invocation](./instance_methods/invocation.md)
+  - [this](./instance_methods/this.md)
+  - [Aliasing](./instance_methods/aliasing.md)
+  - [Derived Values](./instance_methods/derived_values.md)
 
+## Control Flow III
+- [Exceptions]()
+- [Recursion]()
+
+## Code Structure III
+- [Constructors](./constructors.md)
   - [this](./constructors/this.md)
   - [The Default Constructor](./constructors/the_default_constructor.md)
   - [Final Fields](./constructors/final_fields.md)
   - [Multiple Constructors](./constructors/multiple_constructors.md)
+  - [Invariants]()
+- [Multiple Files]()
+- [The Implicit Main Class]()
+- [Private]()
+
+## Data Types IV
 
-- [Instance Methods](./instance_methods.md)
 
-  - [Declaration](./instance_methods/declaration.md)
-  - [Invocation](./instance_methods/invocation.md)
-  - [this](./instance_methods/this.md)
-  - [Aliasing](./instance_methods/aliasing.md)
-  - [Derived Values](./instance_methods/derived_values.md)
 
 - [Documentation]()
   - [Documentation Comments]()

src/arrays.md

@@ -2,7 +2,7 @@
 
 Arrays are used to represent a fixed-size collection of things.
 
-```java
+```java,no_run
 int[] oddNumbers = { 1, 3, 5, 7, 9 };
 ```
 
@@ -14,7 +14,7 @@ We call the things stored in an array its "elements."
 You can make an array of any type of element by using the name of the type followed by
 `[]`.
 
-```java
+```java,no_run
 char[] letters = { 'a', 'b', 'c' };
 String[] words = { "its", "as", "easy", "as" }
 int[] numbers = { 1, 2, 3 };

src/arrays/aliasing.md

@@ -7,6 +7,7 @@ This means that if the contents of the array are updated, that change will
 be reflected by both variables.
 
 ```java
+~void main() {
 char[] lettersOne = { 'B', 'a', 't', 'm', 'a', 'n' };
 char[] lettersTwo = lettersOne;
 
@@ -28,6 +29,7 @@ lettersTwo[0] = 'R';
 System.out.println(lettersOne);
 // Ratman
 System.out.println(lettersTwo);
+~}
 ```
 
 When two variables point to the same thing like this we say that both variables are "aliases"

src/arrays/array_initializers.md

@@ -4,16 +4,16 @@ To give an initial value to an array you can use an array initializer.
 
 After the equals sign you write `{` followed by a comma separated list of elements and a final `}`.
 
-```java
-int[] numbers = { 1, 2, 3 }
+```java,no_run
+int[] numbers = { 1, 2, 3 };
              // |---------|
              // this part is
              // the initializer
 ```
 
 The elements in an initializer do not have to be literals and can also be variables or expressions.
 
-```java
+```java,no_run
 int two = 2;
 // Will hold 1, 2, 3 just like the array above
 int[] numbers = { 1, two, two + 1 }

src/arrays/challenges.md

@@ -9,7 +9,7 @@ Remember the rules for this are
 
 Edit the following program so that the output is zero.
 
-```java
+```java,editable
 void main() {
     // Only change this line
     String[] words = { "Sam", "I", "Am" };
@@ -22,7 +22,7 @@ void main() {
 Using only `System.out.println` and array accesses,
 print `hello world` to the screen.
 
-```java
+```java,editable
 void main() {
     char[] letters = {
         ' ',
@@ -44,7 +44,7 @@ void main() {
 Without editing either the array declaration or the loop at the bottom,
 make the output of this program `0`.
 
-```java
+```java,editable
 void main() {
     final int numbers = { 1, 2, 3, 4 };
 
@@ -68,7 +68,7 @@ void main() {
 Make this program output `bulbasaur` without changing anything
 above or below the marked areas.
 
-```java
+```java,editable
 void main() {
     char[] name = { 'b', 'u', 'l', 'b' };
 

src/arrays/empty_array.md

@@ -19,4 +19,4 @@ System.out.println(emptyCharArray.length);
 
 // Crash
 System.out.println(emptyCharArray[0]);
-```
+```

src/arrays/length.md

@@ -3,13 +3,15 @@
 The number of elements which comprise an array can be accessed by using `.length`.[^unlike_string]
 
 ```java
+~void main() {
 String[] veggies = { "brussels", "cabbage", "carrots" };
 int numberOfElements = veggies.length;
 
 // veggies is 3 elements long
 System.out.println(
-    "veggies is " numberOfElements + " characters long"
+    "veggies is " + numberOfElements + " characters long"
 );
+~}
 ```
 
 [^unlike_string]: Unlike with a `String`, you do not write `()` after `.length`.

src/arrays/printing_the_contents_of_an_array.md

@@ -5,14 +5,17 @@ you won't see the contents of the array. Instead you will see
 something like `[Ljava.lang.String;@1c655221`.
 
 ```java
+~void main() {
 String[] shout = { "fus", "ro", "dah" };
 // [Ljava.lang.String;@5a07e868
 System.out.println(shout);
+~}
 ```
 
 A similar thing will happen with `int[]`, `boolean[]`, and `double[]`.[^gibberish]
 
 ```java
+~void main() {
 int[] nums = { 11, 11, 11 };
 // [I@5a07e868
 System.out.println(nums);
@@ -24,15 +27,18 @@ System.out.println(bools);
 double[] doubles = { 1.1, 1.1, 1.1 };
 // [D@5a07e868
 System.out.println(bools);
+~}
 ```
 
 The only kind of array which will include its contents when printed is a `char[]`.
 It will be printed as if it were a `String`.
 
 ```java
+~void main() {
 char[] continent = { 'T', 'a', 'm', 'r', 'i', 'e', 'l' };
 // Tamriel
 System.out.println(continent);
+~}
 ```
 
 If you want to actually see the contents of an array, you should

src/arrays/reassignment.md

@@ -3,28 +3,36 @@
 The length of an array cannot change, but a variable holding an
 array can be reassigned to a new array that has a different length.
 
+When reassigning the value of an array variable you need to put `new` followed by a space, the type
+of element held by the array, and then `[]` all before the initializer.
+
+So to reassign an `int[]` you need to write something like `new int[] { 1, 2, 3 }`.
+
 ```java
+~void main() {
 int[] numbers = { 1, 2 };
 // 2
 System.out.println(numbers.length);
 
-numbers = { numbers[0], numbers[1], 3 };
+numbers = new int[] { numbers[0], numbers[1], 3 };
 // 3
 System.out.println(numbers.length);
+~}
 ```
 
 This reassignment will not be affect any variables which
 are aliases for the variable's old value.
 
 ```java
+~void main() {
 char[] wordOne = { 'g', 'o' };
 char[] wordTwo = wordOne;
 // go
 System.out.println(wordOne);
 // go
 System.out.println(wordTwo);
 
-wordOne = { wordOne[0], wordOne[1], 's', 'h' };
+wordOne = new int[] { wordOne[0], wordOne[1], 's', 'h' };
 
 // gosh
 System.out.println(wordOne);
@@ -44,4 +52,5 @@ wordOne[0] = 'p';
 System.out.println(wordOne);
 // no
 System.out.println(wordTwo);
+~}
 ```

src/arrays/relation_to_final_variables.md

@@ -6,6 +6,7 @@ This means that the variable cannot be reassigned, but it does not mean
 that the array's contents cannot be changed directly or through an alias.
 
 ```java
+~void main() {
 final char[] catchphrase = { 'w', 'o', 'a', 'h', '!' };
 // woah!
 System.out.println(catchphrase);
@@ -24,4 +25,5 @@ alias[4] = 's';
 
 // egads
 System.out.println(catchphrase);
+~}
 ```