mid.java

mid.java

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;

public class Midterm {

    private final String student_file;

    public Midterm(String student_file) {
        this.student_file = student_file;
    }

    public void display() {
        File file = new File(student_file);

        if (file.exists()) {

            try {
                FileReader fr = new FileReader(file);
                BufferedReader br = new BufferedReader(fr);
                String student;
                while ((student = br.readLine()) != null) {
                    String[] arr = student.split(",");

                    System.out.println(
                            "ID: \t" + arr[0] + "\t " +
                                    "Name: \t" + String.format("%-30s", arr[1].strip()) + "\t " +
                                    "CGPA: \t" + arr[2] + "\t " +
                                    "DOB: \t" + arr[3] + " \t" +
                                    "Gender: " + arr[4]
                    );
                }

                fr.close();
                br.close();

            } catch (IOException ex) {
                ex.printStackTrace();
            }

        }

        System.out.println("File not found.");

    }

    public void displayGender(String gender) {
        File file = new File(student_file);

        try {
            FileReader fr = new FileReader(file);
            BufferedReader br = new BufferedReader(fr);
            String student;

            while ((student = br.readLine()) != null) {
                String[] arr = student.split(",");

                if (arr[4].equals(gender)) {
                    System.out.println(
                            "ID: \t" + arr[0] + "\t " +
                                    "Name: \t" + String.format("%-30s", arr[1].strip()) + "\t " +
                                    "CGPA: \t" + arr[2] + "\t " +
                                    "DOB: \t" + arr[3] + " \t" +
                                    "Gender: " + arr[4]
                    );
                }
            }

            fr.close();
            br.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void displayById(long id) {
        File file = new File(student_file);

        try {
            FileReader fr = new FileReader(file);
            BufferedReader br = new BufferedReader(fr);
            String student;

            while ((student = br.readLine()) != null) {

                String[] arr = student.split(",");

                if (Integer.parseInt(arr[0]) == id) {
                    System.out.println(
                            "ID: \t" + arr[0] + "\t " +
                                    "Name: \t" + String.format("%-30s", arr[1].strip()) + "\t " +
                                    "CGPA: \t" + arr[2] + "\t " +
                                    "DOB: \t" + arr[3] + " \t" +
                                    "Gender: " + arr[4]
                    );
                }
            }
            fr.close();
            br.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }

    }

    public void insert(long id, String name, double cgpa, String dob, String gender) {
        File file = new File(student_file);

        try {
            FileWriter fw = new FileWriter(file, true);

            fw.write(id + "," + String.format("%-30s", name) + "," + cgpa + "," + dob + "," + gender + System.getProperty("line.separator"));

            fw.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void stats() {
        File file = new File(student_file);

        try {
            FileReader fr = new FileReader(file);
            BufferedReader br = new BufferedReader(fr);

            int males = 0;
            int females = 0;

            double mcgpa = 0.0;
            double fcgpa = 0.0;
            String student;

            while ((student = br.readLine()) != null) {

                String[] arr = student.split(",");

                if (arr[4].equals("M"))
                    males++;
                mcgpa += Double.parseDouble(arr[2]);

                if (arr[4].equals("F"))
                    females++;
                fcgpa += Double.parseDouble(arr[2]);

            }

            String str = males + " males cgpa is " + mcgpa / males + "\n" + females + " females cgpa is " + fcgpa / females;
            System.out.println(str);

            fr.close();
            br.close();

            FileWriter fw = new FileWriter("exam.txt");
            fw.write(str);
            fw.close();


        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void delete(long id) {
        File file = new File(student_file);

        if (file.exists()) {
            try {
                FileReader fr = new FileReader(file);
                BufferedReader br = new BufferedReader(fr);

                ArrayList<String> newList = new ArrayList<>();
                String student;

                boolean found = false;

                while ((student = br.readLine()) != null) {
                    String[] arr = student.split(",");

                    if (Integer.parseInt(arr[0]) != id) {
                        newList.add(student);
                    }

                    if (Integer.parseInt(arr[0]) == id) {
                        found = true;
                    }

                }
                fr.close();
                br.close();

                if (found) {
                    FileWriter fw = new FileWriter(student_file);

                    for (String s : newList) {
                        fw.write(s + System.getProperty("line.separator"));
                    }

                    fw.close();
                } else {
                    System.out.println("Student not found.");
                }


            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public void modify(long id, double value) {
        File file = new File(student_file);

        try {
            RandomAccessFile rf = new RandomAccessFile(file, "rw");

            byte[] std_id = new byte[4];
            byte[] record = new byte[55];

            String id_str = null;
            String record_str = null;
            boolean found = false;

            while (rf.getFilePointer() <= rf.length() - 2) {
                rf.read(std_id, 0, 4);
                id_str = new String(std_id);


                if (id_str.equals(String.valueOf(id))) {
                    rf.seek(rf.getFilePointer() + 32);
                    rf.write(String.valueOf(value).getBytes(StandardCharsets.UTF_8));
                    rf.seek(rf.getFilePointer() - 40);
                    rf.read(record, 0, 53);
                    record_str = new String(record);
                    found = true;
                }

                if (found)
                    break;

                rf.seek(rf.getFilePointer() + 50);

            }
            rf.close();
            System.out.println(record_str);

        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void deleteByRandomAccess(long id) {
        File file = new File(student_file);

        try {
            RandomAccessFile rf = new RandomAccessFile(file, "rw");

            boolean found = false;

            byte[] std_id = new byte[4];
            byte[] record = new byte[54];

            String id_Str = null;
            String record_str = null;

            ArrayList<String> newList = new ArrayList<>();

            while (rf.getFilePointer() <= rf.length() - 2) {
                rf.read(std_id, 0, 4);
                id_Str = new String(std_id);

                if (!id_Str.equals(String.valueOf(id))) {

                    rf.seek(rf.getFilePointer() - 4);
                    rf.readLine();
                    rf.seek(rf.getFilePointer() - 54);
                    rf.read(record, 0, 54);
                    record_str = new String(record);
                    newList.add(record_str);

                }

                rf.seek(rf.getFilePointer() + 50);
            }
            rf.close();

            RandomAccessFile rf2 = new RandomAccessFile(file, "rw");
            for (String s : newList) {
                rf2.write(s.getBytes(StandardCharsets.UTF_8));

            }
            rf2.close();

        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void changeExam(long id, String exam, int point) {
        File file = new File("exam.txt");

        try {
            RandomAccessFile rf = new RandomAccessFile(file, "rw");

            byte[] std_id = new byte[8];
            byte[] record = new byte[51];

            String id_str = null;
            String record_str = null;
            boolean found = false;
            long pos = 0;

            switch (exam) {
                case "mt":
                    pos = 32;
                    break;
                case "qz":
                    pos = 35;
                    break;
                case "asg":
                    pos = 38;
                    break;
                case "fin":
                    pos = 41;
                    break;

            }

            while (rf.getFilePointer() <= rf.length() - 2) {
                rf.read(std_id, 0, 8);
                id_str = new String(std_id);

                if (id_str.equals(String.valueOf(id))) {
                    rf.seek(rf.getFilePointer() + pos);
                    rf.write(String.valueOf(point).getBytes(StandardCharsets.UTF_8));
                    found = true;
                }

                if (found)
                    break;

                rf.seek(rf.getFilePointer() + 44);

            }
            rf.close();

        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public void calculateGrades(String input, String output) {
        File file = new File(input);

        if (file.exists()) {
            try {
                FileReader fr = new FileReader(file);
                BufferedReader br = new BufferedReader(fr);

                String student;
                String id = null, grade = null;
                double total = 0.0;
                long mid = 0, quiz = 0, asgn = 0, fin = 0;

                while ((student = br.readLine()) != null) {
                    String[] arr = student.split(",");

                    id = arr[0];
                    mid += Integer.parseInt(arr[2]);
                    quiz += Integer.parseInt(arr[3]);
                    asgn += Integer.parseInt(arr[4]);
                    fin += Integer.parseInt(arr[5]);
                }
                fr.close();
                br.close();

                total = mid * 0.25 + quiz * 0.20 + asgn * 0.10 + fin * 0.45;

                if (total >= 85) {
                    grade = "A";
                } else if (total < 85) {
                    grade = "B";
                } else {
                    grade = "F";
                }

                FileWriter fw = new FileWriter(output);

                fw.write("ID : " + id + "," + "Total : " + total + "," + "Grade : " + grade);

                fw.close();


            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public void writingWithBufferWriter() {
        File file = new File("test.txt");

        try {
            FileWriter fw = new FileWriter(file);
            BufferedWriter bw = new BufferedWriter(fw);

            bw.write("20170001,20170002,20170003,20170004,20170005,20170006,20170007,20170008,20170009,20170010");
            bw.newLine();
            bw.write("mt,mt,mt,mt,mt,mt,mt,mt,mt,mt");
            bw.newLine();
            bw.write("qz,qz,qz,qz,qz,qz,qz,qz,qz,qz");
            bw.newLine();
            bw.write("asg,asg,asg,asg,asg,asg,asg,asg,asg,asg");
            bw.newLine();
            bw.write("fin,fin,fin,fin,fin,fin,fin,fin,fin,fin");
            bw.newLine();
            bw.write("0,0,0,0,0,0,0,0,0,0");
            bw.newLine();
            bw.write("0,0,0,0,0,0,0,0,0,0");
            bw.newLine();
            bw.write("0,0,0,0,0,0,0,0,0,0");
            bw.newLine();
            bw.write("0,0,0,0,0,0,0,0,0,0");
            bw.newLine();

            bw.close();
            fw.close();

        } catch (IOException ex) {
            ex.printStackTrace();
        }


    }
}