Question

In Java. Write a program in a single file that: Main: Creates 10 random doubles, all between 1 and 11, Calls a class that writes 10 random doubles to a text file, one number per line. Calls a class that reads the text file and displays all the doubles and their sum accurate to two decimal places. There has to be three classes, main for create random numbers, one to write , one to read all in the same file

SAMPLE OUTPUT

10.6269119604172
2.737790338909455
5.427925738865128
1.3742058065472509
1.1858700262498836
4.180391276485228
4.910969998930675
5.710858234343958
7.790857007373052
3.1806714736219543

The total is 47.13

The program runs, the main question I have is. what does my professor mean by "in a single file"

Answer 1

In the below program, all the classes (Writer, Reader and Main) are written in the same file, "Main.java" . You can run the program by running Main class.

CODE :

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

class Writer{
    public void write(double arr[]) throws IOException {
        //Writer to write to file
        BufferedWriter writer = new BufferedWriter(new FileWriter(new File("doubles.txt")));
        //Iterate through double array
        for(int i=0;i<arr.length;i++){
            //Write to file
            writer.write(String.valueOf(arr[i]));
            //Write to next line
            if(i!=arr.length-1){
                writer.write("\n");
            }
        }
        writer.flush();
        writer.close();
    }
}

class Reader{
    public double getSum() throws IOException {
        //Reader to read file
        BufferedReader br = new BufferedReader(new FileReader(new File("doubles.txt")));
        String str;
        double ans = 0;
        //Read all lines
        while((str=br.readLine())!=null){
            //Find sum
            ans = ans + Double.parseDouble(str);
        }
        return ans;
    }
}

class Main{
    public static void main(String[] args) throws IOException {
        Random r = new Random();
        double arr[] = new double[10];
        //Generate 10 randoms from 1 to 11
        for(int i=0;i<10;i++){
            arr[i] = 10*r.nextDouble()+1;
            System.out.println(arr[i]);
        }
        Writer w = new Writer();
        w.write(arr);
        Reader rd = new Reader();
        System.out.println("Total is "+rd.getSum());
    }
}

OUTPUT :