diff --git a/CarQueue.java b/CarQueue.java
new file mode 100644
index 0000000..3510ca8
--- /dev/null
+++ b/CarQueue.java
@@ -0,0 +1,26 @@
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class CarQueue {
+    public static void main(String[] args) {
+        Queue<String> carQueue = new LinkedList<>();
+
+        carQueue.add("BMW");
+        carQueue.add("Toyota");
+        carQueue.add("Honda");
+
+        System.out.println("Queue: " + carQueue);
+        String firstCar = carQueue.poll();
+        System.out.println("Queue: " + carQueue);
+        String secondCar = carQueue.poll();
+        System.out.println("Queue: " + carQueue);
+        String thirdCar = carQueue.poll();
+        System.out.println("Queue: " + carQueue);
+        
+        if (carQueue.isEmpty()) {
+            System.out.println("Empty.");
+        } else {
+            System.out.println("Not Empty.");
+        }
+    }
+}
diff --git a/HashCollisionChecker.java b/HashCollisionChecker.java
index 80631a7..783ae2f 100644
--- a/HashCollisionChecker.java
+++ b/HashCollisionChecker.java
@@ -2,13 +2,19 @@
 
 public class HashCollisionChecker {
     public static <T> int countOfUniqueHashCodes(HashSet<T> set) {
-        // TODO: Implement
-        return 0;
+        HashSet<Integer> hashCodes = new HashSet<>();
+        for (T item : set) {
+            hashCodes.add(item.hashCode());
+        }
+        return hashCodes.size();
     }
 
     public static <K, V> int countOfUniqueHashCodes(HashMap<K, V> map) {
-        // TODO: Implement
-        return 0;
+        HashSet<Integer> hashCodes = new HashSet<>();
+        for (K key : map.keySet()) {
+            hashCodes.add(key.hashCode());
+        }
+        return hashCodes.size();
     }
 
     public static void main(String[] args) {
diff --git a/ShuffleLinkedList.java b/ShuffleLinkedList.java
new file mode 100644
index 0000000..176ac7b
--- /dev/null
+++ b/ShuffleLinkedList.java
@@ -0,0 +1,17 @@
+import java.util.Collections;
+import java.util.LinkedList;
+
+public class ShuffleLinkedList {
+    public static void main(String[] args) {
+        LinkedList<Object> list = new LinkedList<>();
+        list.add(45);
+        list.add("GFG");
+        list.add(2.56f);
+        list.add(3.14);
+        list.add("Ali");
+        list.add(true);
+        System.out.println("Before: " + list.toString());
+        Collections.shuffle(list);
+        System.out.println("After: " + list.toString());
+    }
+}
diff --git a/Detective.java b/ToDos.java
similarity index 69%
rename from Detective.java
rename to ToDos.java
index 5707416..3757e3d 100644
--- a/Detective.java
+++ b/ToDos.java
@@ -1,7 +1,7 @@
  
 import java.util.ArrayList;
 
-class ToDos {
+public class ToDos {
     
   public static void main(String[] args) {
     
@@ -25,10 +25,18 @@ public static void main(String[] args) {
     poirotsToDos.add("reveal the truth of the crime");
     
     // Print the size of each ArrayList below:
-
+    System.out.println("Sherlock: " + sherlocksToDos.size());
+    System.out.println("Poirot: " + poirotsToDos.size());
     
       
     // Print the name of the detective with the larger to-do list:
+   if (sherlocksToDos.size() > poirotsToDos.size()) {
+            System.out.println("Sherlock.");
+    } else if (sherlocksToDos.size() < poirotsToDos.size()) {
+        System.out.println("Poirot.");
+    } else {
+        System.out.println("Equal.");
+    }
     
   }
   
diff --git a/University.java b/University.java
new file mode 100644
index 0000000..221efdd
--- /dev/null
+++ b/University.java
@@ -0,0 +1,61 @@
+import java.util.TreeSet;
+
+class Student implements Comparable<Student> {
+    private int id;
+    private String name;
+    private double moadel;
+
+    public Student(int id, String name, double moadel) {
+        this.id = id;
+        this.name = name;
+        this.moadel = moadel;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public double getMoadel() {
+        return moadel;
+    }
+
+    @Override
+    public int compareTo(Student other) {
+        return Integer.compare(this.id, other.id);
+    }
+}
+
+public class University {
+    private TreeSet<Student> students;
+
+    public University() {
+        students = new TreeSet<>();
+    }
+
+    public void addStudent(int id, String name, double moadel) {
+        students.add(new Student(id, name, moadel));
+    }
+
+    public String searchStudentById(int id) {
+        for (Student student : students) {
+            if (student.getId() == id) {
+                return "Name: " + student.getName() + ", Moadel: " + student.getMoadel();
+            }
+        }
+        return "Student not found.";
+    }
+
+    public static void main(String[] args) {
+        University university = new University();
+        university.addStudent(1, "Hasan", 3.5);
+        university.addStudent(2, "Shima", 3.8);
+        university.addStudent(3, "Amir", 3.9);
+
+        System.out.println(university.searchStudentById(2));
+        System.out.println(university.searchStudentById(4));
+    }
+}