Question

import java.util.Scanner;
// TASK #1 Add the file I/O import statement here

/**
   This class reads numbers from a file, calculates the
   mean and standard deviation, and writes the results
   to a file.
*/

public class StatsDemo
{
   // TASK #1 Add the throws clause
   public static void main(String[] args)
   {
      double sum = 0;      // The sum of the numbers
      int count = 0;       // The number of numbers added
      double mean = 0;     // The average of the numbers
      double stdDev = 0;   // The standard deviation
      String line;         // To hold a line from the file
      double difference;   // The value and mean difference

      // Create an object of type Scanner
      Scanner keyboard = new Scanner (System.in);
      String filename;     // The user input file name

      // Prompt the user and read in the file name
      System.out.println("This program calculates " +
                         "statistics on a file " +
                         "containing a series of numbers");
      System.out.print("Enter the file name:  ");
      filename = keyboard.nextLine();

Answer 1

Solution

Code

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;

/**
This class reads numbers from a file, calculates the
mean and standard deviation, and writes the results
to a file.
*/

public class Main
{

public static void main(String[] args) throws IOException
{
double sum = 0; // The sum of the numbers
int count = 0; // The number of numbers added
double mean = 0; // The average of the numbers
double stdDev = 0; // The standard deviation
String line; // To hold a line from the file
double difference; // The value and mean difference
ArrayList<Double> values = new ArrayList<>();

Scanner keyboard = new Scanner (System.in);
String filename;

System.out.println("This program calculates " +
"statistics on a file " +
"containing a series of numbers");
System.out.print("Enter the file name: ");
filename = keyboard.nextLine();
keyboard.close();
  
FileReader File = new FileReader(filename);
BufferedReader readFile = new BufferedReader(File);
line = readFile.readLine();
while(true){
   line = readFile.readLine();
   if(line == null)
       break;
   else{
       values.add(Double.parseDouble(line));
       sum += Double.valueOf(line);
   count += 1;
   }  
}
readFile.close();
System.out.println(count);
mean = sum / count;
  
FileReader File_read = new FileReader(filename);
BufferedReader read_File = new BufferedReader(File_read);
sum = 0; count = 0;
line = read_File.readLine();
while(true){
   line = read_File.readLine();
   if(line == null)
       break;
   else{
       difference = (Double.valueOf(line) - mean);
       sum += Math.pow(difference, 2);
       count += 1;
   }
}
read_File.close();
stdDev = Math.sqrt(sum / count - 1);
  
FileWriter write = new FileWriter("Result.txt");
PrintWriter output = new PrintWriter(write);
output.printf("Mean of %s = %.3f.\n\n", values.toString(), mean);
output.printf("Standard Deviation of %s = %.3f.",values.toString(), stdDev);
output.close();
}
}

Screenshot

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all the best