Some stuff done

src/main/java/rocks/zipcode/io/quiz4/collections/ComparableTreeSet.java

@@ -5,14 +5,18 @@ package rocks.zipcode.io.quiz4.collections;
  */
 public class ComparableTreeSet<_> {
     public ComparableTreeSet(_... arr) {
-    }
 
+    }
 
-    
     public ComparableTreeSet() {
+        
     }
 
     public Integer compareTo(ComparableTreeSet<_> o) {
         return null;
     }
+
+    public String toString(){
+        return null;
+    }
 }

src/main/java/rocks/zipcode/io/quiz4/collections/ZipCodeWilmington.java

@@ -2,20 +2,29 @@ package rocks.zipcode.io.quiz4.collections;
 
 import rocks.zipcode.io.quiz4.objectorientation.Student;
 
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.Map;
 
 /**
  * @author leon on 11/12/2018.
  */
 public class ZipCodeWilmington {
+
+    private ArrayList<Student> students = new ArrayList<>();
+
     public void enroll(Student student) {
+        this.students.add(student);
     }
 
     public Boolean isEnrolled(Student student) {
-        return null;
+        return this.students.contains(student);
     }
 
     public void lecture(double numberOfHours) {
+        for(Student i : students){
+            i.learn(numberOfHours/students.size());
+        }
     }
 
     public Map<Student, Double> getStudyMap() {

src/main/java/rocks/zipcode/io/quiz4/fundamentals/StringEvaluator.java

@@ -1,11 +1,26 @@
 package rocks.zipcode.io.quiz4.fundamentals;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
 /**
  * @author leon on 11/12/2018.
  */
 public class StringEvaluator {
     public static String[] getAllPrefixes(String string) {
-        return null;
+
+        String[] output = new String[(string.length() - 1 )*(string.length() - 1)];
+        int count = 0;
+
+        for(int i = 0; i < string.length() - 1; i++){
+            for(int j = 0; j < string.length() - 1; j++){
+                output[count] = (string.substring(i, j));
+                count++;
+            }
+        }
+
+        return output;
     }
 
     public static String[] getCommonPrefixes(String string1, String string2) {

src/main/java/rocks/zipcode/io/quiz4/objectorientation/Student.java

@@ -4,17 +4,23 @@ package rocks.zipcode.io.quiz4.objectorientation;
  * @author leon on 11/12/2018.
  */
 public class Student {
+
+    private Double totalStudyTime;
+    private Integer id;
+
     public Student() {
-        this(null);
+        this.id = null;
     }
 
     public Student(Integer id) {
+        this.id = id;
     }
 
     public void learn(Double amountOfHours) {
+        totalStudyTime =+ amountOfHours;
     }
 
     public Double getTotalStudyTime() {
-        return null;
+        return this.totalStudyTime;
     }
-}
+}