LAB 3

package statsdemo;
import java.util.Scanner;
import java.io.*; 

public class StatsDemo {
    // TASK #1 Add the throws clause  
    
    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();

        //------------------------------------------------------------ TASK 2
        
	// ADD LINES FOR TASK #2 HERE 
        // Create a File object passing it the filename 
        File file = new File(filename);
        // Create a Scanner object passing File object 
        Scanner inputFile = new Scanner(file);
        // Perform a priming read to read the first line of  the file 
        line = inputFile.nextLine();
        // Loop until you are at the end of the file 
        while(inputFile.hasNext()){
    	  if(line == null)
    		  break;
    	  else{
                // Add value to sum 
    		 sum += Double.parseDouble(line);
                 // Increment the counter 
        	 count += 1; 
                 // Read a new line from the file 
                 line = inputFile.nextLine();
    	  }	
      }

        // Close the input file 
        inputFile.close();
        // Store the calculated mean 
        mean = (sum)/(count);
        //------------------------------------------------------------ TASK 3
        
	// ADD LINES FOR TASK #3 HERE 
        // Reconnect File object passing it the filename 
        file = new File(filename);
        // Reconnect Scanner object passing File object 
        inputFile = new Scanner(file);
        // Reinitialize the sum of the numbers 
        sum = 0;
        // Reinitialize the number of numbers added 
        count = 0;
        // Perform a priming read to read the first line of the file 
        line = inputFile.nextLine();
        // Loop until you are at the end of the file 
        while(inputFile.hasNext()){
    	  if(line == null)
    	    break;
    	  else{
            // subtract the mean 
            difference = (Double.parseDouble(line) - mean);
            // Add the square of the difference to the sum 
    	    sum += Math.pow(difference, 2);
            // Increment the counter 
            count += 1; 
            // Read a new line from the file 
            line = inputFile.nextLine();
    	  }	
      }
        
        // Close the input file 
        inputFile.close();
        // Store the calculated standard deviation  
        stdDev = Math.sqrt(sum / count);
        //------------------------------------------------------------ TASK 1
        
        // ADD LINES FOR TASK #1 HERE 
        // Create a FileWriter object using "Results.txt" 
        FileWriter fw = new FileWriter("Results.txt", true);
        // Create a PrintWriter object passing the FileWriter object 
        PrintWriter pw = new PrintWriter(fw);
        // Print the results to the output file 
        pw.printf("Mean = %.3f.\n", mean);
        pw.printf("Standard Deviation = %.3f.\n", stdDev);
        pw.close();
        
        // Close the output file 
    } 
}