//import statemnts for Random, Scanner and IO import java.util.Random; import java.util.Scanner; import java.io.*; public class Hobbits { public static void main(String[] args) throws IOException { final int NUM_HOBBITS = 5; final int NUM_COLUMNS = 2; String fileName = "hobbits.csv"; //call populateHobbits( ) to create the two dimensional array double[][] hobbits = populateHobbits(NUM_HOBBITS, NUM_COLUMNS); //display the number of hobbits System.out.println(hobbits.length + " hobbits accepted Gandalf's invitation to lunch\n"); //calculate the means of the columns double[] hobbitMeans = getColMeans(hobbits); //write hobbits array to file writeHobbits(hobbits, fileName); //read and display the file that has been read readHobbitses(fileName); //call displayColMeans to display hobbit means displayColMeans(hobbitMeans); } //method to populate hobbits array with random double values public static double[][] populateHobbits(int numHobbits, int numCols) { final double HT_MULTIPLIER = 10.0; //multiplier for the hobbit height final double WT_MULTIPLIER = 250.0; //multiplier for the hobbit weight //instantiate Random object Random rand = new Random(); //declare two dim array with numHobbits rows numCols columns double[][] hobbitArray = new double[numHobbits][numCols]; //assign random double values to all elements for (int i = 0; i < numHobbits; i++) //outer loop is for rows { for (int j = 0; j < numCols; j++) //inner loop is for columns { //get a random double value in range [0.2, 0.4] double randDouble = getRandDouble(rand); //assign this double to the current array element hobbitArray[i][j] = randDouble; //determine which multiplier to use if (j == 0) //this is column for height hobbitArray[i][j] *= HI_MULTIPLIER; else //this is column for weight hobbitArray[i][j] *= WT_MULTIPLIER; } } return hobbitArray; //return the two dimensional array } //method to write hobbits array to file public static void writeHobbits(double[][] ar, String fileName) throws IOException { //open the file to write PrintWriter outFile = new PrintWriter(fileName); //print columen heading of the array of stats outFile.println("HEIGHT,WEIGHT"); for (int i = 0; i < ar.length; i++) { for (int j = 0; j < ar[i].length; j++) { outFile.print(ar[i][j]); //if at end of a row, add newline char if (j == ar[i].length - 1) outFile.print("\n"); else //add the "," delimiter outFile.print(","); } //end of inner loop } //end of outer loop outFile.close(); //close outfile System.out.println("The file was successfully written\n"); } //end of method //method to read the hobbits file public static void readHobbitses(String fileName) throws IOException { //open the file to read File dataFile = new File(fileName); Scanner inFile = new Scanner(dataFile); //variable to contain the substrings of one line of file String[] oneLine = new String[2]; int counter = 0; //keep track of line numbers System.out.println("Data read from the " + fileName + " file:"); //read file, one line at a time while (inFile.hasNe.

1. //import statemnts for Random, Scanner and IO
import java.util.Random;
import java.util.Scanner;
import java.io.*;
public class Hobbits
{
public static void main(String[] args) throws IOException
{
final int NUM_HOBBITS = 5;
final int NUM_COLUMNS = 2;
String fileName = "hobbits.csv";
//call populateHobbits( ) to create the two dimensional array
double[][] hobbits = populateHobbits(NUM_HOBBITS, NUM_COLUMNS);
//display the number of hobbits
System.out.println(hobbits.length + " hobbits accepted Gandalf's invitation to lunchn");
//calculate the means of the columns
double[] hobbitMeans = getColMeans(hobbits);
//write hobbits array to file
writeHobbits(hobbits, fileName);
//read and display the file that has been read
readHobbitses(fileName);
//call displayColMeans to display hobbit means
displayColMeans(hobbitMeans);
}
//method to populate hobbits array with random double values
public static double[][] populateHobbits(int numHobbits, int numCols)
{
final double HT_MULTIPLIER = 10.0; //multiplier for the hobbit height
final double WT_MULTIPLIER = 250.0; //multiplier for the hobbit weight
//instantiate Random object
Random rand = new Random();
//declare two dim array with numHobbits rows numCols columns
double[][] hobbitArray = new double[numHobbits][numCols];

2. //assign random double values to all elements
for (int i = 0; i < numHobbits; i++) //outer loop is for rows
{
for (int j = 0; j < numCols; j++) //inner loop is for columns
{
//get a random double value in range [0.2, 0.4]
double randDouble = getRandDouble(rand);
//assign this double to the current array element
hobbitArray[i][j] = randDouble;
//determine which multiplier to use
if (j == 0) //this is column for height
hobbitArray[i][j] *= HI_MULTIPLIER;
else //this is column for weight
hobbitArray[i][j] *= WT_MULTIPLIER;
}
}
return hobbitArray; //return the two dimensional array
}
//method to write hobbits array to file
public static void writeHobbits(double[][] ar, String fileName) throws IOException
{
//open the file to write
PrintWriter outFile = new PrintWriter(fileName);
//print columen heading of the array of stats
outFile.println("HEIGHT,WEIGHT");
for (int i = 0; i < ar.length; i++)
{
for (int j = 0; j < ar[i].length; j++)
{
outFile.print(ar[i][j]);
//if at end of a row, add newline char
if (j == ar[i].length - 1)
outFile.print("n");
else //add the "," delimiter
outFile.print(",");
} //end of inner loop
} //end of outer loop
outFile.close(); //close outfile

3. System.out.println("The file was successfully writtenn");
} //end of method
//method to read the hobbits file
public static void readHobbitses(String fileName) throws IOException {
//open the file to read
File dataFile = new File(fileName);
Scanner inFile = new Scanner(dataFile);
//variable to contain the substrings of one line of file
String[] oneLine = new String[2];
int counter = 0; //keep track of line numbers
System.out.println("Data read from the " + fileName + " file:");
//read file, one line at a time
while (inFile.hasNext()) {
String dataLine = inFile.nextLine();
oneLine = dataLine.split(","); //split line with delimiter
if (counter > 0) //for second line and beyond, format doubles
{
System.out.printf("%.2ftt%.2fn", Double.parseDouble(oneLine[0]),
Double.parseDouble(oneLine[1]));
} else //if this first line, display the column heading
System.out.println(oneLine[0] + "t" + oneLine[1]);
if (inFile.hasNext())
counter++; //keep track of how many lines
} //end while loop read file
inFile.close(); //close the file
System.out.println("The file has now been successfully read.n");
} //end of method
//method to determine average values of columns two dim array
public static double[] getColMeans(double[][] ar) {
//local array to store means
//array is sized according to length second dimension of parameter
//first element is mean of first column
//second element is mean of second column, etc
double[] meanAr = new double[ar[0].length];

4. //nested for loop to iterate through elements in parameter
for (int i = 0; i < ar.length; i++) {
for (int j = 0; j < ar[i].length; j++) {
//sum the elements in the current column
meanAr[j] += ar[i][j];
}
} //end of outer loop
//replace the sum with the average; i.e. divide by number of rows
for (int i = 0; i < meanAr.length; i++)
meanAr[i] /= ar.length;
Lab16 Sample output