Feature/calculator

src/Features/Calculator.java

@@ -0,0 +1,21 @@
+public class Calculator {
+
+    public double add(double a, double b) {
+        return a + b;
+    }
+
+    public double subtract(double a, double b) {
+        return a - b;
+    }
+
+    public double multiply(double a, double b) {
+        return a * b;
+    }
+
+    public double divide(double a, double b) {
+        if (b == 0.0) {
+            throw new IllegalArgumentException("Division by zero");
+        }
+        return a / b;
+    }
+}

src/Features/Student.java

@@ -0,0 +1,80 @@
+public class Student {
+
+    private String id;
+    private String name;
+    private String email;
+    private String department;
+    private double gpa;
+
+    // No-arg constructor
+    public Student() {
+    }
+
+    // Parameterized constructor
+    public Student(String id, String name, String email, String department, double gpa) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+        this.department = department;
+        this.gpa = gpa;
+    }
+
+    // Copy constructor
+    public Student(Student other) {
+        if (other != null) {
+            this.id = other.id;
+            this.name = other.name;
+            this.email = other.email;
+            this.department = other.department;
+            this.gpa = other.gpa;
+        }
+    }
+
+    // Getters
+    public String getId() { return id; }
+    public String getName() { return name; }
+    public String getEmail() { return email; }
+    public String getDepartment() { return department; }
+    public double getGpa() { return gpa; }
+
+    // Setters
+    public void setId(String id) { this.id = id; }
+    public void setName(String name) { this.name = name; }
+    public void setEmail(String email) { this.email = email; }
+    public void setDepartment(String department) { this.department = department; }
+    public void setGpa(double gpa) {
+        if (gpa < 0.0) gpa = 0.0;
+        if (gpa > 4.0) gpa = 4.0;
+        this.gpa = gpa;
+    }
+
+    // Convenience builder-style methods (optional chaining)
+    public Student withId(String id) { setId(id); return this; }
+    public Student withName(String name) { setName(name); return this; }
+    public Student withEmail(String email) { setEmail(email); return this; }
+    public Student withDepartment(String department) { setDepartment(department); return this; }
+    public Student withGpa(double gpa) { setGpa(gpa); return this; }
+
+    @Override
+    public String toString() {
+        return "Student{id='" + id + '\'' +
+               ", name='" + name + '\'' +
+               ", email='" + email + '\'' +
+               ", department='" + department + '\'' +
+               ", gpa=" + gpa +
+               '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Student)) return false;
+        Student s = (Student) o;
+        return (id != null && id.equals(s.id));
+    }
+
+    @Override
+    public int hashCode() {
+        return id == null ? 0 : id.hashCode();
+    }
+}