studentDB.java

package Arrays;

public class studentDB {
    private String user;
    private String pass;
    private student[] db = new student[10];
    private boolean checkLogin;
    private int size;

    public studentDB() {}

    public studentDB(String user, String pass) {
        this.user = user;
        this.pass = pass;
        System.out.println("DB Created");
    }

    public boolean login(String user, String pass) {
        if (user.equals(this.user) && pass.equals(this.pass)) {
            checkLogin = true;
            System.out.println("LogIn Success");
            return true;
        }
        System.out.println("Invalid Credentials");
        return false;
    }

    public boolean addStudent(String name, int age, int year, String degree, int marks, String blood, char gender, int roll) {
        if (checkLogin) {
            if (size < db.length*0.7) {
                db[size] = new student(name, age, year, degree,marks, blood, gender, roll);
                size++;
       
                return true;
            } else {
                student[] temp = new student[db.length * 2];
                for (int i = 0; i < size; i++) {
                    temp[i] = db[i];
                }
                db = temp; 
                db[size] = new student(name, age, year, degree, marks, blood, gender, roll);
                size++;
                System.out.println(name + " Student Added (after resize)!");
                return true;
            }
        }
        System.out.println("Please Log In");
        return false;
    }

    public void printDB() {
        if (checkLogin) {
            for (int i = 0; i < size; i++) {
                System.out.println(db[i]);
            }
        } else {
            System.out.println("Please Login");
        }
    }

    public boolean searchByName(String name) {
        if (checkLogin) {
            for (int i = 0; i < size; i++) {
                if (db[i].name.equalsIgnoreCase(name)) {
                    return true;
                }
            }
        }
        return false;
    }

    public void searchByRoll() {
        if (checkLogin) {
            for (int i = 0; i < size - 1; i++) {
                for (int j = 0; j < size - 1 - i; j++) {
                    if (db[j].roll > db[j + 1].roll) {
                        student temp = db[j];
                        db[j] = db[j + 1];
                        db[j + 1] = temp;
                    }
                }
            }
        } 
        else
        {
            System.out.println("Please LogIn");
        }
    }

    public boolean removeByName(String name) {
        if (checkLogin) {
            int i;
            for (i = 0; i < size; i++) {
                if (db[i].name.equals(name)) {
                    break;
                }
            }
            if (i < size) {
                student[] temp = new student[db.length - 1];
                for (int j = 0, k = 0; j < size; j++) {
                    if (j != i) {
                        temp[k++] = db[j];
                    }
                }
                db = temp;
                size--;
                System.out.println(name + " removed from DB");
                return true;
            } else {
                System.out.println("Student Not Found");
                return false;
            }
        }
        return false;
        
    }
    
//    public void sortByName() {
//        if (checkLogin) {
//            for (int i = 0; i < size - 1; i++) {
//                for (int j = 0; j < size - 1 - i; j++) {
//                    if (db[j].name.compareToIgnoreCase(db[j + 1].name) > 0) {
//                        // swap
//                        student temp = db[j];
//                        db[j] = db[j + 1];
//                        db[j + 1] = temp;
//                    }
//                }
//            }
//            System.out.println("Students sorted by Name.");
//        } else {
//            System.out.println("Please Login");
//        }
//    }
    public void sortByMarks() {
        if (checkLogin) {
            for (int i = 0; i < size - 1; i++) {
                for (int j = 0; j < size - 1 - i; j++) {
                    if (db[j].marks < db[j + 1].marks) { 
                        // swap (bada marks pehle aayega)
                        student temp = db[j];
                        db[j] = db[j + 1];
                        db[j + 1] = temp;
                    }
                }
            }
            System.out.println("Students sorted by Marks (High to Low).");
        } else {
            System.out.println("Please Login");
        }
    }


}