Student Management System

Programs/studentManagement/Student.java

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+//student data model
+package Programs.studentManagement;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class Student {
+        //private accessed via getter setter
+        private String id;
+        private String name;
+        private int age;
+        private String faculty;
+        private String email;
+
+        /*Email verification regex:
+         * Basic format: 
+         * ^: Asserts the start of the string.
+         * [a-zA-Z0-9_+&*-]+: Matches one or more alphanumeric characters, plus _, +, &, *, and - for the local part (username) of the email.
+        (?:\\.[a-zA-Z0-9_+&*-]+)*: Optionally matches additional parts of the local part, separated by a dot (.). The (?: ... ) creates a non-capturing group.
+        @: Matches the literal @ symbol.
+        (?:[a-zA-Z0-9-]+\\.)+: Matches one or more domain components, each consisting of alphanumeric characters and hyphens, followed by a dot (.).
+        [a-zA-Z]{2,7}: Matches the top-level domain (TLD), which must be 2 to 7 alphabetic characters long. This range is a common practice, but specific TLDs can be longer or shorter. 
+        $: Asserts the end of the string.
+         */
+        private static final String EMAIL_FORMAT = "(?=^.{4,40}$)[A-Za-z0-9._%+\\-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,7}$";; //compiles te given regex string into pattern that can be used to reated matcher obj.
+        private static final Pattern EMAIL_PATTERN = Pattern.compile(EMAIL_FORMAT, Pattern.CASE_INSENSITIVE);
+
+        //No-arg constructor for creating obj tht will be populated later
+        //E.g: Student s = new Student();
+        public Student() {}
+
+        //E.g: Student s = new Student(id, name, age, email, faculty);
+        public Student(String id, String name, int age, String email, String faculty) {
+            this.id = id;
+            this.name = name;
+            //apply validation for age and email for range and format check
+            setAge(age);
+            setEmail(email); 
+            this.faculty = faculty;
+        }
+
+        //getter setup for each field to read values
+        public String getId() {
+            return id;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public int getAge() {
+            return age;
+        }
+
+        public String getEmail() {
+            return email;
+        }
+
+        public String getFaculty() {
+            return faculty;
+        }
+
+        //setter setup for each field to update values
+        public void setId(String id ) {
+            this.id = id;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public void setAge(int age) {
+            if (age<=15 || age>23) {
+                throw new IllegalArgumentException("Age must be between 15 and 23 for college students.");
+            } else {
+                this.age = age;
+            }
+        }
+
+        public void setEmail(String email) {
+            if (email == null) {
+                throw new IllegalArgumentException("Email must not be null.");
+            }
+            String trimmed = email.trim(); //remove leading/trailing whitespace
+            Matcher m = EMAIL_PATTERN.matcher(trimmed);
+            if (!m.matches()) {
+                throw new IllegalArgumentException("Email format is invalid.");
+            }
+            // Enforce gmail.com domain to catch typos like "@gmail.xom"
+            String lower = trimmed.toLowerCase();
+            if (!lower.endsWith("@gmail.com")) {
+                throw new IllegalArgumentException("Only gmail.com address are accepted.");
+            }
+            this.email = trimmed;
+        }
+
+        public void setFaculty(String faculty) {
+            this.faculty = faculty;
+        }
+    }
+

Programs/studentManagement/StudentManager.java

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+//store and manage Student objects 
+package Programs.studentManagement;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.List;
+
+public class StudentManager {
+    //HashMap to store students with ID as key for quick lookup
+    private final Map<String, Student> students = new HashMap<>();
+
+    //check existence by ID
+    public boolean studentExists(String id) {
+        if (id == null) return false;
+        return students.containsKey(id.trim());
+    }
+
+    public boolean addStudent(Student s) {
+        if ( s == null || s.getId() == null || s.getId().trim().isEmpty()) {
+            throw new IllegalArgumentException("Student or Student ID cannot be null/empty.");
+        }
+        String id = s.getId().trim();
+        if (students.containsKey(id) || findByEmail(s.getEmail()) != null){
+            return false; //student with same ID exists
+        }
+
+        //duplicate name (case-insensitive)
+        if (s.getName() != null && findByName(s.getName()) != null) {
+            return false;
+        }
+
+        String email = s.getEmail();
+        if ( email == null)  {
+            return false;
+        } else {
+            students.put(id, s);
+            return true; //successfully added
+        }
+
+    }
+
+    public Student findById(String id) {
+        if ( id == null) return null;
+        return students.get(id);
+    } 
+
+    //Linear search for email.Normalizes by trimming and lower-casting
+    public Student findByEmail(String email) {
+        if ( email == null) return null;
+        String norm = normalizedEmail(email);
+        for (Student s : students.values()) {
+            String sEmail = normalizedEmail(s.getEmail());
+            if (sEmail != null && norm.equals(normalizedEmail(sEmail))) {
+                return s;
+            }
+        }
+        return null;
+    } 
+
+    public Student findByName(String name) {
+        if ( name == null) return null;
+        String norm = normalizedName(name);
+        if (norm == null) return null;
+        for (Student s : students.values()) {
+            String sName = s.getName();
+            if (sName != null && norm.equals(normalizedName(sName))) {
+                return s;
+            }
+        }
+        return null;
+
+    }
+
+    public boolean updateStudent(Student updated) {
+        if ( updated == null || updated.getId() == null ) {
+            throw new IllegalArgumentException("Student and id must not be empty.");
+        }
+        String id = updated.getId();
+        if (!students.containsKey(id)) {
+            return false;
+        }
+        Student updatedEmail = findByEmail(updated.getEmail());
+
+        if (updatedEmail != null && !updatedEmail.getId().equals(id)) {
+            return false; //another stude
+        }
+
+        //name conflict nt has this email
+        if (updated.getName() != null) {
+            Student ownName = findByName(updated.getName());
+            if (ownName != null && !ownName.getId().equals(id)) {
+                return false;
+            }
+        }
+
+        students.put(id, updated);
+        return true;
+    }
+
+    public boolean deleteStudents(String id) {
+        if ( id == null ) return false;
+        return students.remove(id) != null;
+    }
+
+    public List<Student> listAll() {
+        return new ArrayList<>(students.values()); 
+    }
+
+    //helpers method
+    private String normalizedEmail(String email) {
+        if ( email == null) return null;
+        return email.trim().toLowerCase();
+    }
+
+    public String normalizedName(String name) {
+        if (name == null) return null;
+        return name.trim().toLowerCase();
+    }
+}