Java Lab Task #4 Calculating the Mean 1) Now we need to add lines to allow us to
ID: 3601676 • Letter: J
Question
Java Lab
Task #4 Calculating the Mean
1) Now we need to add lines to allow us to read from the input file and calculate the mean.
-Create a File object passing it the filename.
-Create a Scanner object passing it the File object.
2) Write a priming read to read the first line of the file.
3) Write a loop that continues until you are at the end of the file (see Example 4-19 on page 241-242 of textbook)
4) The body of the loop will:
-convert the line into a double value and add the value to the accumulator
-increment the counter
-read a new line from the file
4) When the program exits the loop close the input file.
5) Calculate and store the mean. The mean is calculated by dividing the accumulator by the counter.
6) Compile, debug, and run. You should now get a mean of 77.444, but the standard deviation will still be 0.000.
///
Code Listing 4.2 (StatsDemo.java)
import java.util.Scanner;
// TASK #3 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 #3 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();
// ADD LINES FOR TASK #4 HERE
// Create a File object passing it the filename
// Create a Scanner object passing File object
// Perform a priming read to read the first line
//of the file
// Loop until you are at the end of the file
// Convert the line to a double value and add the
// value to sum
// Increment the counter
// Read a new line from the file
// Close the input file
// Store the calculated mean
// ADD LINES FOR TASK #5 HERE
// Reconnect File object passing it the
// filename
// Reconnect Scanner object passing
// File object
// Reinitialize the sum of the numbers
// Reinitialize the number of numbers added
// Perform a priming read to read the first line of
// the file
// Loop until you are at the end of the file
// Convert the line into a double value and
// subtract the mean
// Add the square of the difference to the sum
// Increment the counter
// Read a new line from the file
// Close the input file
// Store the calculated standard deviation
// ADD LINES FOR TASK #3 HERE
// Create a FileWriter object using "Results.txt"
// Create a PrintWriter object passing the// FileWriter object
// Print the results to the output file
// Close the output file
}
}
Explanation / Answer
Hi,
here is the complete code for all the tasks with comments to help you understand.
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
public class StatsDemo {
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
// 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();
File file = new File(filename);//creating a file object
Scanner sc = new Scanner(file);//passing it to scanner to read file
while (sc.hasNextLine()) {//loop till EOF reached
double i = sc.nextDouble();//getting double value
sum+=i;//adding to sum
count++;//incrementing counter
}
sc.close();//closing file
mean=sum/count;//calculating mean
sum=0;//re initializing sum and count
count=0;
sc = new Scanner(file);//passing file again
while (sc.hasNextLine()) {//loop till EOF reached
double i = sc.nextDouble();//getting double value
sum+=(i-mean)*(i-mean);//squaring difference by mean
count++;
}
sc.close();
stdDev=Math.sqrt(sum/count-1);//calculating std deviation
File file1 = new File("Result.txt");// new o/p file object
// creates the file
file1.createNewFile();
// creates a FileWriter Object
FileWriter writer = new FileWriter(file1);
PrintWriter out = new PrintWriter(writer); //print write object
// Write to the file
out.println(mean);
out.println(stdDev);
// Close the file.
out.close();
keyboard.close();
}
}
Thumbs up if this was helpful, otherwise let me know in comments
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.