Read two text files and write specific lines from those two text files into a third file

Question

I am creating a hospital management system in which I have 2 classes namely AddDoctor and AddPatient which takes the input from user about their details and stores them into their respective files. I now want to create an Appointment class in which I can assign a patient with a certain ID to a doctor with a certain ID which are read from the files. This would be very easy if Java supported multiple inheritance, but since it doesn't, I'm stuck on how I could do this task.

Following is my AddDoctor class

class AddDoctor{
    int did;
    int dage;
    long dphno;
    String dname;
    String dgender;
    String dqualification;

    InputStreamReader in = new InputStreamReader(System.in);
    BufferedReader br = new BufferedReader(in);

    void input() throws IOException{
        System.out.print("Enter Doctor's Name:");
        dname = br.readLine();

        Random rand = new Random();
        did = rand.nextInt((9999 - 100) + 1) + 10;

        System.out.print("Enter Doctor's Phone Number:");
        dphno = Long.parseLong(br.readLine());

        System.out.print("Enter Doctor's Age:");
        dage = Integer.parseInt(br.readLine());

        System.out.print("Enter Doctor's Gender:");
        dgender = br.readLine();

        System.out.print("Enter Doctor's Qualification:");
        dqualification = br.readLine();
    }

    void delete() throws FileNotFoundException, IOException{
        Scanner in = new Scanner(System.in);
        File inputFile = new File("DoctorDetails.txt");
        File tempFile = new File("myTemp.txt");

        BufferedReader reader = new BufferedReader(new FileReader(inputFile));
        BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

        String currentLine;

        String lineToRemove;
        System.out.println("Enter the ID of the Doctor you wish to delete: ");
        lineToRemove = in.next();

        while((currentLine = reader.readLine()) != null) {
            String trimmedLine = currentLine.trim();
            if(trimmedLine.startsWith(lineToRemove)) continue;          
            writer.write((currentLine) + System.getProperty("line.separator"));
        }
        writer.close();
        reader.close();
        Files.move(tempFile.toPath(), inputFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
    }

    void search() throws IOException{
        Scanner scan=new Scanner(System.in);
        System.out.println("Enter the ID of the Doctor To Search:");
        String did=scan.next();
        String line="";
        try{
            FileInputStream fin = new FileInputStream("DoctorDetails.txt");
            Scanner sc = new Scanner(fin);
            while(sc.hasNextLine()){
                line=sc.nextLine();
                if(line.startsWith(did))
                    System.out.println(line+" ");
            }
            sc.close();
        }
        catch(IOException e){
            e.printStackTrace();
        }
    }
    
    void display(){
        try{
            BufferedReader br=new BufferedReader(new FileReader("DoctorDetails.txt"));
            String s="";
            while((s=br.readLine())!=null){
                String data[]=new String[6];
                data=s.split(" ");
                for(int i=0;i<6;i++){
                    System.out.print(data[i]+"\t");
                }
                System.out.println();
            }
            br.close();
        }
        catch(Exception e){
        }
    }
};


//Class WriteD to Write Doctor Details in a text file where the details are fetched from the Class AddDoctor
class WriteD extends AddDoctor {
        void write() {
            try(FileWriter fw = new FileWriter("DoctorDetails.txt",true);
                BufferedWriter bw = new BufferedWriter(fw);
                PrintWriter out = new PrintWriter(bw))
                {
                    out.println(did + " " + dname + " " + dphno + " " + dage + " " + dgender + " " + dqualification);
                }catch(IOException e){
                e.printStackTrace();
                }
        }
    };

Following is my AddPatient Class

    class AddPatient extends People{
    String pillness;
    String pregisterdate;

    InputStreamReader in = new InputStreamReader(System.in);
    BufferedReader br = new BufferedReader(in);

    void input() throws IOException{
        System.out.print("Enter Patient's Name:");
        name = br.readLine();

        Random rand1 = new Random();
        id = rand1.nextInt((9999 - 100) + 1) + 10;

        System.out.print("Enter Patient's Phone Number:");
        phno = Long.parseLong(br.readLine());

        System.out.print("Enter Patient's Age:");
        age = Integer.parseInt(br.readLine());

        System.out.print("Enter Patient's Gender:");
        gender = br.readLine();

        System.out.print("Enter Patient's Illness:");
        pillness = br.readLine();

        System.out.print("Enter Patient's Registration Date:");
        pregisterdate = br.readLine();
    }

    void delete() throws FileNotFoundException, IOException{
        Scanner in = new Scanner(System.in);
        File inputFile = new File("PatientDetails.txt");
        File tempFile = new File("myTemp2.txt");

        BufferedReader reader = new BufferedReader(new FileReader(inputFile));
        BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

        String currentLine;

        String lineToRemove;
        System.out.println("Enter the ID of the Patient you wish to delete: ");
        lineToRemove = in.next();

        while((currentLine = reader.readLine()) != null) {
            String trimmedLine = currentLine.trim();
            if(trimmedLine.startsWith(lineToRemove)) continue;
            writer.write((currentLine) + System.getProperty("line.separator"));
        }
        writer.close();
        reader.close();
        Files.move(tempFile.toPath(), inputFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
    }

    void search() throws IOException{
        Scanner scan=new Scanner(System.in);
        System.out.println("Enter the ID of the Patient To Search:");
        String did=scan.next();
        String line="";
        try{
            FileInputStream fin = new FileInputStream("PatientDetails.txt");
            Scanner sc = new Scanner(fin);
            while(sc.hasNextLine()){
                line=sc.nextLine();
                if(line.startsWith(did))
                    System.out.println(line);
            }
            sc.close();
        }
        catch(IOException e){
            e.printStackTrace();
        }
    }

    void display(){
        try{
            BufferedReader br=new BufferedReader(new FileReader("PatientDetails.txt"));
            String s="";
            while((s=br.readLine())!=null){
                String data[]=new String[7];
                data=s.split(" ");
                for(int i=0;i<7;i++){
                    System.out.print(data[i]+"\t");
                }
                System.out.println();
            }
            br.close();
        }
        catch(Exception e){
        }
    }
};

    class WriteP extends AddPatient {
        void write() {
                try(FileWriter fw = new FileWriter("PatientDetails.txt",true);
                    BufferedWriter bw = new BufferedWriter(fw);
                    PrintWriter out = new PrintWriter(bw))
                    {
                        out.println(String.format("%-1s %-1s %-1s %-1s %-1s %-1s %-1s",id,name,phno,age,gender,pillness,pregisterdate));
                    }catch(IOException e){
                    e.printStackTrace();
                    }
            }
        };

Answer 1

Simple solution is using composition create object of doc and patient in appointment class and get doc and patient id from user or create one using objects and write it in third file.

In case of Id you need to search info from file. In case of new information, as you will be creating object of doctor and patient. first right them in their files and then store data in third file as you want.

If it answer your question let me know.