diff --git a/src/main/java/BigDecimalUtils.java b/src/main/java/BigDecimalUtils.java
new file mode 100644
index 0000000..766f803
--- /dev/null
+++ b/src/main/java/BigDecimalUtils.java
@@ -0,0 +1,18 @@
+public class BigDecimalUtils {
+    /**
+     * Rounds the given BigDecimal to the nearest hundredth and returns a double.
+     */
+    public static double roundToHundredths(java.math.BigDecimal value) {
+        if (value == null) return 0.0;
+        return value.setScale(2, java.math.RoundingMode.HALF_UP).doubleValue();
+    }
+
+    /**
+     * Reverses the sign of the given BigDecimal, rounds to nearest tenth, and returns a double.
+     */
+    public static double reverseSignAndRoundToTenth(java.math.BigDecimal value) {
+        if (value == null) return 0.0;
+        java.math.BigDecimal reversed = value.negate();
+        return reversed.setScale(1, java.math.RoundingMode.HALF_UP).doubleValue();
+    }
+}
diff --git a/src/main/java/Car.java b/src/main/java/Car.java
new file mode 100644
index 0000000..608d573
--- /dev/null
+++ b/src/main/java/Car.java
@@ -0,0 +1,17 @@
+public abstract class Car {
+    protected String vinNumber;
+    protected String make;
+    protected String model;
+    protected int mileage;
+
+    public Car(String vinNumber, String make, String model, int mileage) {
+        this.vinNumber = vinNumber;
+        this.make = make;
+        this.model = model;
+        this.mileage = mileage;
+    }
+
+    public String getInfo() {
+        return String.format("VIN: %s, Make: %s, Model: %s, Mileage: %d", vinNumber, make, model, mileage);
+    }
+}
diff --git a/src/main/java/IntArrayList.java b/src/main/java/IntArrayList.java
new file mode 100644
index 0000000..b70d470
--- /dev/null
+++ b/src/main/java/IntArrayList.java
@@ -0,0 +1,32 @@
+import java.util.Arrays;
+
+public class IntArrayList implements IntList {
+    private int[] data;
+    private int size;
+
+    public IntArrayList() {
+        this.data = new int[10];
+        this.size = 0;
+    }
+
+    @Override
+    public void add(int number) {
+        ensureCapacity();
+        data[size++] = number;
+    }
+
+    private void ensureCapacity() {
+        if (size >= data.length) {
+            int newLength = data.length + data.length / 2; // 50% larger
+            data = Arrays.copyOf(data, newLength);
+        }
+    }
+
+    @Override
+    public int get(int id) {
+        if (id < 0 || id >= size) {
+            throw new IndexOutOfBoundsException();
+        }
+        return data[id];
+    }
+}
diff --git a/src/main/java/IntList.java b/src/main/java/IntList.java
new file mode 100644
index 0000000..3a3835c
--- /dev/null
+++ b/src/main/java/IntList.java
@@ -0,0 +1,4 @@
+public interface IntList {
+    void add(int number);
+    int get(int id);
+}
diff --git a/src/main/java/IntVector.java b/src/main/java/IntVector.java
new file mode 100644
index 0000000..8f24957
--- /dev/null
+++ b/src/main/java/IntVector.java
@@ -0,0 +1,32 @@
+import java.util.Arrays;
+
+public class IntVector implements IntList {
+    private int[] data;
+    private int size;
+
+    public IntVector() {
+        this.data = new int[20];
+        this.size = 0;
+    }
+
+    @Override
+    public void add(int number) {
+        ensureCapacity();
+        data[size++] = number;
+    }
+
+    private void ensureCapacity() {
+        if (size >= data.length) {
+            int newLength = data.length * 2;
+            data = Arrays.copyOf(data, newLength);
+        }
+    }
+
+    @Override
+    public int get(int id) {
+        if (id < 0 || id >= size) {
+            throw new IndexOutOfBoundsException();
+        }
+        return data[id];
+    }
+}
diff --git a/src/main/java/Main.java b/src/main/java/Main.java
new file mode 100644
index 0000000..024dd45
--- /dev/null
+++ b/src/main/java/Main.java
@@ -0,0 +1,37 @@
+import java.math.BigDecimal;
+
+public class Main {
+    public static void main(String[] args) {
+        // BigDecimal utilities demo
+        BigDecimal bd1 = new BigDecimal("4.2545");
+        System.out.println("Rounded to hundredths: " +
+                BigDecimalUtils.roundToHundredths(bd1)); // 4.25
+
+        BigDecimal bd2 = new BigDecimal("1.2345");
+        System.out.println("Reverse sign & round to tenth: " +
+                BigDecimalUtils.reverseSignAndRoundToTenth(bd2)); // -1.2
+
+        // Car hierarchy demo
+        Car sedan = new Sedan("1HGBH41JXMN109186", "Toyota", "Camry", 30000);
+        System.out.println(sedan.getInfo());
+        Car uv = new UtilityVehicle("2FTRX18W1XCA12345", "Ford", "Explorer", 45000, true);
+        System.out.println(uv.getInfo());
+        Car truck = new Truck("3C6UR5FL8GE123456", "RAM", "2500", 120000, 7500.0);
+        System.out.println(truck.getInfo());
+
+        // Video hierarchy demo
+        Video series = new TvSeries("Stranger Things", 50, 25);
+        System.out.println(series.getInfo());
+        Video movie = new Movie("Inception", 148, 8.8);
+        System.out.println(movie.getInfo());
+
+        // IntList demos
+        IntList arrayList = new IntArrayList();
+        for (int i = 0; i < 12; i++) arrayList.add(i);
+        System.out.println("IntArrayList[5] = " + arrayList.get(5));
+
+        IntList vector = new IntVector();
+        for (int i = 0; i < 25; i++) vector.add(i * 2);
+        System.out.println("IntVector[20] = " + vector.get(20));
+    }
+}
diff --git a/src/main/java/Movie.java b/src/main/java/Movie.java
new file mode 100644
index 0000000..fdbf19f
--- /dev/null
+++ b/src/main/java/Movie.java
@@ -0,0 +1,13 @@
+public class Movie extends Video {
+    private double rating;
+
+    public Movie(String title, int duration, double rating) {
+        super(title, duration);
+        this.rating = rating;
+    }
+
+    @Override
+    public String getInfo() {
+        return super.getInfo() + ", Rating: " + rating;
+    }
+}
diff --git a/src/main/java/Sedan.java b/src/main/java/Sedan.java
new file mode 100644
index 0000000..a455d98
--- /dev/null
+++ b/src/main/java/Sedan.java
@@ -0,0 +1,5 @@
+public class Sedan extends Car {
+    public Sedan(String vinNumber, String make, String model, int mileage) {
+        super(vinNumber, make, model, mileage);
+    }
+}
diff --git a/src/main/java/Truck.java b/src/main/java/Truck.java
new file mode 100644
index 0000000..9c99220
--- /dev/null
+++ b/src/main/java/Truck.java
@@ -0,0 +1,13 @@
+public class Truck extends Car {
+    private double towingCapacity;
+
+    public Truck(String vinNumber, String make, String model, int mileage, double towingCapacity) {
+        super(vinNumber, make, model, mileage);
+        this.towingCapacity = towingCapacity;
+    }
+
+    @Override
+    public String getInfo() {
+        return super.getInfo() + ", TowingCapacity: " + towingCapacity;
+    }
+}
diff --git a/src/main/java/TvSeries.java b/src/main/java/TvSeries.java
new file mode 100644
index 0000000..467af03
--- /dev/null
+++ b/src/main/java/TvSeries.java
@@ -0,0 +1,13 @@
+public class TvSeries extends Video {
+    private int episodes;
+
+    public TvSeries(String title, int duration, int episodes) {
+        super(title, duration);
+        this.episodes = episodes;
+    }
+
+    @Override
+    public String getInfo() {
+        return super.getInfo() + ", Episodes: " + episodes;
+    }
+}
diff --git a/src/main/java/UtilityVehicle.java b/src/main/java/UtilityVehicle.java
new file mode 100644
index 0000000..c4d4ee0
--- /dev/null
+++ b/src/main/java/UtilityVehicle.java
@@ -0,0 +1,13 @@
+public class UtilityVehicle extends Car {
+    private boolean fourWheelDrive;
+
+    public UtilityVehicle(String vinNumber, String make, String model, int mileage, boolean fourWheelDrive) {
+        super(vinNumber, make, model, mileage);
+        this.fourWheelDrive = fourWheelDrive;
+    }
+
+    @Override
+    public String getInfo() {
+        return super.getInfo() + ", FourWheelDrive: " + fourWheelDrive;
+    }
+}
diff --git a/src/main/java/Video.java b/src/main/java/Video.java
new file mode 100644
index 0000000..4567e1b
--- /dev/null
+++ b/src/main/java/Video.java
@@ -0,0 +1,13 @@
+public abstract class Video {
+    protected String title;
+    protected int duration; // in minutes
+
+    public Video(String title, int duration) {
+        this.title = title;
+        this.duration = duration;
+    }
+
+    public String getInfo() {
+        return String.format("Title: %s, Duration: %d minutes", title, duration);
+    }
+}