Question

• The program reads a text file with student records (first name, last name and grade on each line) and determines their type (excellent or ok). <--- Completed
• Need help on this
• Then it prompts the user to enter a command, executes the command and loops. The commands are the following:
• • "all" - prints all student records (first name, last name, grade, type).
  • "excellent" - prints students with grade > 89.
  • "ok" - prints students with grade <= 89.
  • "end" - exits the loop the terminates the program.

import java.util.Scanner;
import java.io.*;
import java.util.ArrayList;

public class Students
{
public static void main (String[] args) throws IOException
{ String first_name, last_name;
int grade, count=0;
Scanner fileInput = new Scanner(new File("students.txt"));
//Object st;
ArrayList<Student> st = new ArrayList<Student>();
while (fileInput.hasNext())
{
first_name = fileInput.next();
last_name = fileInput.next();
grade = fileInput.nextInt();

if (grade>89)
st.add(new Excellent(first_name, last_name, grade));
else
st.add(new Ok(first_name, last_name, grade));

count++;
}
  
for (int i=0; i<st.size(); i++)
{
if (st.get(i) instanceof Excellent)
st.get(i).info();
else
st.get(i).info();
}   
  
System.out.println("There are " + count + " students");
  
}
}

public class Ok implements Student
{
private String fname, lname;
private int grade;
  
public Ok(String fname, String lname, int grade)
{
this.fname = fname;
this.lname = lname;
this.grade = grade;
}

public void info()
{
System.out.println(fname + " " + lname + " "+ grade + "\t" + "ok");
}
}

public class Excellent implements Student
{
private String fname, lname;
private int grade;

public Excellent(String fname, String lname, int grade)
{
this.fname = fname;
this.lname = lname;
this.grade = grade;
}

public void info()
{
System.out.println(fname + " " + lname + " "+ grade + "\t" + "excellent");
}
}

public interface Student
{
void info();
}

Answer 1

Thanks for the question.

Below is the code you will be needing  Let me know if you have any doubts or if you need anything to change.

I have assumed the text file is a comma separated file, incase it is space separated file replace the below line as 

String[] tokens = line.split(",");

to

String[] tokens = line.split("\\s+");


Thank You !!

===========================================================================


public class Student {

    private String firstName;
    private String lastName;
    private int grade;

    public Student(String firstName, String lastName, int grade) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.grade = grade;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getGrade() {
        return grade;
    }

    public void setGrade(int grade) {
        this.grade = grade;
    }

    @Override
    public String toString() {
        return "Name: " + firstName + " " + lastName + ", Grade: " + grade;
    }
}

=============================================================

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

public class Students {

    public static void main(String[] args) {

        String fileName = "students.txt";
        ArrayList<Student> records = null;
        try {
            records = getDataFromFile(fileName);
        } catch (FileNotFoundException e) {
            System.out.println("Unable to read data from file: " + fileName);
            System.exit(1);
        }

        String input;
        Scanner sc = new Scanner(System.in);
        System.out.println("\"all\" - prints all students");
        System.out.println("\"excellent\" - prints all students grade>89");
        System.out.println("\"ok\" - prints all students grade<=89");
        System.out.println("\"end\" - exit program");
        while (true) {

            System.out.println("Enter your command here > ");
            input = sc.nextLine();
            if (input.equals("all")) {
                for (Student student : records) System.out.println(student);
            }else if(input.equals("excellent")){
                for(Student student:records){
                    if(student.getGrade()>89) System.out.println(student);
                }
            }else if(input.equals("ok")){
                for(Student student:records){
                    if(student.getGrade()<=89) System.out.println(student);
                }
            }else if(input.equals("end"))break;
            else System.out.println("Invalid command please try again.");

        }


    }

    private static ArrayList<Student> getDataFromFile(String fileName) throws FileNotFoundException {

        Scanner fileScanner = new Scanner(new File(fileName));
        ArrayList<Student> students = new ArrayList<Student>();

        while (fileScanner.hasNext()) {
            String line = fileScanner.nextLine();
            //System.out.println(line);
            // assummed the data a separated by comma in the file
            String[] tokens = line.split(",");
            int grade = Integer.parseInt(tokens[2].trim());

            students.add(new Student(tokens[0].trim(), tokens[1].trim(), grade));

        }
        fileScanner.close();
        return students;

    }
}