diff --git a/src/main/java/me/alex4386/gachon/sw14462/Main.java b/src/main/java/me/alex4386/gachon/sw14462/Main.java
index 1744a5d..02af3f1 100644
--- a/src/main/java/me/alex4386/gachon/sw14462/Main.java
+++ b/src/main/java/me/alex4386/gachon/sw14462/Main.java
@@ -5,7 +5,7 @@
 import java.util.*;
 
 public class Main {
-    public static String currentTarget = "day18";
+    public static String currentTarget = "day20";
     public static boolean fallbackToLatest = true;
 
     public static Map<String, Class<?>> getAvailableTargetClassNames() {
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/Main.java
new file mode 100644
index 0000000..1568b88
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/Main.java
@@ -0,0 +1,18 @@
+package me.alex4386.gachon.sw14462.day20;
+
+import me.alex4386.gachon.sw14462.utils.Chainloader;
+
+public class Main {
+    public static String chainloadTarget = "ex10_7";
+
+    public static void main(String[] args) throws Throwable {
+        String packageName = Main.class.getPackage().getName();
+        String chainLoadTargetClass = packageName + "." + chainloadTarget + ".Main";
+
+        try {
+            Chainloader.chainloadTarget(chainLoadTargetClass, args);
+        } catch (Exception e) {
+            throw e;
+        }
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Circle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Circle.java
new file mode 100644
index 0000000..cc6c88d
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Circle.java
@@ -0,0 +1,22 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1a;
+
+public class Circle extends Shape {
+    private double radius;
+
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    @Override
+    public double getArea() {
+        return Math.PI * Math.pow(radius, 2);
+    }
+
+    public String toString() {
+        return "Circle: radius=" + radius;
+    }
+
+    public boolean equals(Circle obj) {
+        return this.radius == obj.radius;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Main.java
new file mode 100644
index 0000000..5fa3dc8
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Main.java
@@ -0,0 +1,16 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1a;
+public class Main {
+    public static void main(String[] args) {
+        Shape[] shapes = new Shape[4];
+        shapes[0] = new Rectangle(10, 20);
+        shapes[1] = new Circle(10);
+        shapes[2] = new RightTriangle(10, 20);
+        shapes[3] = new Circle(6);
+
+        for (Shape s : shapes) {
+            System.out.println(s);
+            System.out.println("Area: " + s.getArea());
+            System.out.println();
+        }
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Rectangle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Rectangle.java
new file mode 100644
index 0000000..d277ed5
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Rectangle.java
@@ -0,0 +1,25 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1a;
+
+public class Rectangle extends Shape {
+    private double width;
+    private double height;
+
+    public Rectangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height;
+    }
+
+    @Override
+    public String toString() {
+        return "Rectangle: width=" + width + ", height=" + height;
+    }
+
+    public boolean equals(Rectangle obj) {
+        return this.width == obj.width && this.height == obj.height;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/RightTriangle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/RightTriangle.java
new file mode 100644
index 0000000..47464e0
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/RightTriangle.java
@@ -0,0 +1,25 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1a;
+
+public class RightTriangle extends Shape {
+    private double width;
+    private double height;
+
+    public RightTriangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height / 2;
+    }
+
+    @Override
+    public String toString() {
+        return "RightTriangle: width=" + width + ", height=" + height;
+    }
+
+    public boolean equals(RightTriangle obj) {
+        return this.width == obj.width && this.height == obj.height;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Shape.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Shape.java
new file mode 100644
index 0000000..2610740
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1a/Shape.java
@@ -0,0 +1,7 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1a;
+
+public abstract class Shape {
+    public double getArea() {
+        return 0.0;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Circle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Circle.java
new file mode 100644
index 0000000..043f4e8
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Circle.java
@@ -0,0 +1,22 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1b;
+
+public class Circle implements Shape {
+    private double radius;
+
+    public Circle(double radius) {
+        this.radius = radius;
+    }
+
+    @Override
+    public double getArea() {
+        return Math.PI * Math.pow(radius, 2);
+    }
+
+    public String toString() {
+        return "Circle: radius=" + radius;
+    }
+
+    public boolean equals(Circle obj) {
+        return this.radius == obj.radius;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Main.java
new file mode 100644
index 0000000..340f110
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Main.java
@@ -0,0 +1,17 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1b;
+
+public class Main {
+    public static void main(String[] args) {
+        Shape[] shapes = new Shape[4];
+        shapes[0] = new Rectangle(10, 20);
+        shapes[1] = new Circle(10);
+        shapes[2] = new RightTriangle(10, 20);
+        shapes[3] = new Circle(6);
+
+        for (Shape s : shapes) {
+            System.out.println(s);
+            System.out.println("Area: " + s.getArea());
+            System.out.println();
+        }
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Rectangle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Rectangle.java
new file mode 100644
index 0000000..1a03c24
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Rectangle.java
@@ -0,0 +1,25 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1b;
+
+public class Rectangle implements Shape {
+    private double width;
+    private double height;
+
+    public Rectangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height;
+    }
+
+    @Override
+    public String toString() {
+        return "Rectangle: width=" + width + ", height=" + height;
+    }
+
+    public boolean equals(Rectangle obj) {
+        return this.width == obj.width && this.height == obj.height;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/RightTriangle.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/RightTriangle.java
new file mode 100644
index 0000000..f978f3f
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/RightTriangle.java
@@ -0,0 +1,25 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1b;
+
+public class RightTriangle implements Shape {
+    private double width;
+    private double height;
+
+    public RightTriangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height / 2;
+    }
+
+    @Override
+    public String toString() {
+        return "RightTriangle: width=" + width + ", height=" + height;
+    }
+
+    public boolean equals(RightTriangle obj) {
+        return this.width == obj.width && this.height == obj.height;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Shape.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Shape.java
new file mode 100644
index 0000000..0655575
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1b/Shape.java
@@ -0,0 +1,5 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1b;
+
+public interface Shape {
+    public double getArea();
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/HazardPay.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/HazardPay.java
new file mode 100644
index 0000000..a1ccbde
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/HazardPay.java
@@ -0,0 +1,12 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1c;
+
+public class HazardPay extends PayCalculator {
+    public HazardPay(double payRate) {
+        this.payRate = payRate;
+    }
+
+    @Override
+    public double computePay(double hours) {
+        return super.computePay(hours) * 1.5;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/Main.java
new file mode 100644
index 0000000..fd69834
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/Main.java
@@ -0,0 +1,11 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1c;
+
+public class Main {
+    public static void main(String[] args) {
+        PayCalculator regularPay = new RegularPay(10);
+        PayCalculator hazardPay = new HazardPay(10);
+
+        System.out.println("Regular Pay: " + regularPay.computePay(10));
+        System.out.println("Hazard Pay: " + hazardPay.computePay(10));
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/PayCalculator.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/PayCalculator.java
new file mode 100644
index 0000000..38e39e4
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/PayCalculator.java
@@ -0,0 +1,10 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1c;
+
+public abstract class PayCalculator {
+    protected double payRate;
+
+    public double computePay(double hours) {
+        return this.payRate * hours;
+    }
+
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/RegularPay.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/RegularPay.java
new file mode 100644
index 0000000..5b7423b
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1c/RegularPay.java
@@ -0,0 +1,7 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1c;
+
+public class RegularPay extends PayCalculator {
+    public RegularPay(double payRate) {
+        this.payRate = payRate;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/Main.java
new file mode 100644
index 0000000..509cad2
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/Main.java
@@ -0,0 +1,15 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1d;
+
+public class Main {
+    public static void main(String[] args) {
+        MessageEncoder[] encoders = new MessageEncoder[2];
+        encoders[0] = new ShuffleCipher(1);
+        encoders[1] = new SubstitutionCipher(3);
+
+        String plainText = "All your base are belong to us.";
+        System.out.println("Original Message: " + plainText);
+        for (MessageEncoder encoder : encoders) {
+            System.out.println("Encoded Message ("+encoder.getClass().getName().substring(encoder.getClass().getName().lastIndexOf('.') + 1)+"): " + encoder.encode(plainText));
+        }
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/MessageEncoder.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/MessageEncoder.java
new file mode 100644
index 0000000..5fc8810
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/MessageEncoder.java
@@ -0,0 +1,5 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1d;
+
+public interface MessageEncoder {
+    public String encode(String plainText);
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/ShuffleCipher.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/ShuffleCipher.java
new file mode 100644
index 0000000..87d2151
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/ShuffleCipher.java
@@ -0,0 +1,49 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1d;
+
+public class ShuffleCipher implements MessageEncoder {
+    private int n;
+
+    public ShuffleCipher(int n) {
+        this.n = n;
+    }
+
+    @Override
+    public String encode(String plainText) {
+        char[] plainTextArray = plainText.toCharArray();
+        char[] encodedTextArray = new char[plainTextArray.length];
+
+        for (int i = 0; i < this.n; i++) {
+            encodedTextArray = shuffle(plainTextArray);
+        }
+
+        return new String(encodedTextArray);
+    }
+
+    private char[] shuffle(char[] plainTextArray) {
+        char[] encodedTextArray = new char[plainTextArray.length];
+
+        // split into two arrays
+        char[] firstHalf = new char[plainTextArray.length / 2 + 1];
+        char[] secondHalf = new char[plainTextArray.length - firstHalf.length];
+
+        // alternate between first and second half
+        for (int i = 0; i < plainTextArray.length; i++) {
+            if (i < firstHalf.length) {
+                firstHalf[i] = plainTextArray[i];
+            } else {
+                secondHalf[i - firstHalf.length] = plainTextArray[i];
+            }
+        }
+
+        // merge two arrays with alternating patterns
+        for (int i = 0; i < plainTextArray.length; i++) {
+            if (i % 2 == 0) {
+                encodedTextArray[i] = firstHalf[i / 2];
+            } else {
+                encodedTextArray[i] = secondHalf[i / 2];
+            }
+        }
+
+        return encodedTextArray;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/SubstitutionCipher.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/SubstitutionCipher.java
new file mode 100644
index 0000000..f32107a
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_1d/SubstitutionCipher.java
@@ -0,0 +1,32 @@
+package me.alex4386.gachon.sw14462.day20.ex10_1d;
+
+public class SubstitutionCipher implements MessageEncoder {
+    private int shift;
+
+    public SubstitutionCipher(int shift) {
+        this.shift = shift;
+    }
+
+    @Override
+    public String encode(String plainText) {
+        StringBuilder encodedText = new StringBuilder();
+
+        for (int i = 0; i < plainText.length(); i++) {
+            char c = plainText.charAt(i);
+            if (c >= 'A' && c <= 'Z') {
+                c = (char) (c + shift);
+                if (c > 'Z') {
+                    c = (char) (c - 26);
+                }
+            } else if (c >= 'a' && c <= 'z') {
+                c = (char) (c + shift);
+                if (c > 'z') {
+                    c = (char) (c - 26);
+                }
+            }
+            encodedText.append(c);
+        }
+
+        return encodedText.toString();
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Main.java
new file mode 100644
index 0000000..2c39bac
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Main.java
@@ -0,0 +1,39 @@
+package me.alex4386.gachon.sw14462.day20.ex10_7;
+
+import java.util.Arrays;
+
+public class Main {
+
+    private static<T> void printSorting (T[] arr) {
+        System.out.println("Before Sorting:");
+        for (T t : arr) {
+            System.out.println(t);
+        }
+
+        System.out.println();
+        Arrays.sort(arr);
+
+        System.out.println("After Sorting:");
+        for (T t : arr) {
+            System.out.println(t);
+        }
+        System.out.println();
+    }
+
+    public static void main(String[] args) {
+        Student[] students = new Student[3];
+        students[0] = new Student("Bob", 2);
+        students[1] = new Student("Alex", 3);
+        students[2] = new Student("Charlie", 1);
+
+        printSorting(students);
+
+        System.out.println("Converting to StudentLexical for Lexical Sorting");
+        StudentLexical[] studentsLexical = new StudentLexical[3];
+        for (int i = 0; i < students.length; i++) {
+            studentsLexical[i] = new StudentLexical(students[i]);
+        }
+
+        printSorting(studentsLexical);
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Person.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Person.java
new file mode 100644
index 0000000..1f3cbc9
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Person.java
@@ -0,0 +1,35 @@
+package me.alex4386.gachon.sw14462.day20.ex10_7;
+
+public class Person
+{
+    private String name;
+    public Person()
+    {
+        name = "No name yet";
+    }
+
+    public Person(String initialName)
+    {
+        name = initialName;
+    }
+
+    public void setName(String newName)
+    {
+        name = newName;
+    }
+
+    public String getName()
+    {
+        return name;
+    }
+
+    public void writeOutput()
+    {
+        System.out.println("Name: " + name);
+    }
+
+    public boolean hasSameName(Person otherPerson)
+    {
+        return this.name.equalsIgnoreCase(otherPerson.name);
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Student.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Student.java
new file mode 100644
index 0000000..aeabedc
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/Student.java
@@ -0,0 +1,58 @@
+package me.alex4386.gachon.sw14462.day20.ex10_7;
+
+public class Student extends Person implements Comparable
+{
+    private int studentNumber;
+    public Student()
+    {
+        super();
+        studentNumber = 0;//Indicating no number yet
+    }
+    public Student(String initialName, int initialStudentNumber)
+    {
+        super(initialName);
+        studentNumber = initialStudentNumber;
+    }
+    public void reset(String newName, int newStudentNumber)
+    {
+        setName(newName);
+        studentNumber = newStudentNumber;
+    }
+    public int getStudentNumber()
+    {
+        return studentNumber;
+    }
+    public void setStudentNumber(int newStudentNumber)
+    {
+        studentNumber = newStudentNumber;
+    }
+    public void writeOutput()
+    {
+        System.out.println("Name: " + getName());
+        System.out.println("Student Number: " + studentNumber);
+    }
+    public boolean equals(Student otherStudent)
+    {
+        return this.hasSameName(otherStudent) &&
+                (this.studentNumber == otherStudent.studentNumber);
+    }
+
+    @Override
+    public int compareTo(Object o) {
+        Student otherStudent = (Student) o;
+        if (this.studentNumber < otherStudent.studentNumber) {
+            return -1;
+        } else if (this.studentNumber == otherStudent.studentNumber) {
+            return 0;
+        } else {
+            return 1;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Name: " + getName() + ", Student Number: " + studentNumber;
+    }
+}
+
+
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/StudentLexical.java b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/StudentLexical.java
new file mode 100644
index 0000000..5727ae2
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day20/ex10_7/StudentLexical.java
@@ -0,0 +1,17 @@
+package me.alex4386.gachon.sw14462.day20.ex10_7;
+
+public class StudentLexical extends Student implements Comparable
+{
+
+    public StudentLexical(Student student) {
+        super(student.getName(), student.getStudentNumber());
+    }
+
+    @Override
+    public int compareTo(Object o) {
+        StudentLexical otherStudent = (StudentLexical) o;
+        return this.getName().compareTo(otherStudent.getName());
+    }
+}
+
+