lab4: Loops and Files Lab Objectives Be able to write a while loop Be able to wr
ID: 3846422 • Letter: L
Question
lab4:
Loops and Files
Lab Objectives
Be able to write a while loop
Be able to write a do-while loop
Be able to write a for loop
Be able to use file streams for I/O
Be able to write a loop that reads until end of file
Be able to implement an accumulator and a counter
Introduction
This is a simulation of rolling dice. We will roll 10,000 times in our program. The theoretical
probability of rolling doubles of a specific number is 1 out of 36 or approximately 278 out of
10,000 times that you roll the pair of dice. Since this is a simulation, the numbers will vary a
little each time you run it. We will start with a while loop, then use the same program, changing
the while loop to a do-while loop, and then a for loop.
We will be introduced to file input and output. We will read a file, line by line, converting each
line into a number. We will then use the numbers to calculate the mean and standard deviation.
Task #1 Loops
1. Copy the file DiceSimulation.java into NetBeans or other Java IDE tools.
2. The double roll of 1s and 2s are given in the code. You can run the program to get a
result like:
Comment Prompt:
C: MyWorkhomework>java Dicesimulation
You rolled snake eyes 279 out of 10000 rolls.
You rolled double twos 275 out of 10000 rolls.
You rolled double threes 0 out of 10000 rolls.
You rolled double fours 0 out of 10000 rolls.
You rolled double sixes 0 out of 10000 rolls.
C: MyWorkhomework>
3. You follow the style to code for double roll value for 3 – 6 so all the doubles should be
around 278.
4. Change the while loop to do-while loop and run the program. Result should be similar.
5. Change the while loop to a for loop and run the program. Result should be similar.
Task #2 File Input and Output
1. Copy the files StatsDemo.java into NetBeans or other Java IDE tools.
2. Read “FilePath.doc” to know where to put the Numbers.txt.
3. The file input and output part is coded. Try to read through the code and understand the
program.
4. Try to run the program. Enter Numbers.txt when prompted. Check the Result.txt. There
should be just one line on the file to show “mean = 0.000”.
5. Modify the program to calculate the mean. Run the program. You should now get a mean
of 77.444 in the Result.txt
FilePath:
When dealing with files, file path is a key point.
1. Absolute file path – You can give input/output file an absolute file path so that the Java program knows where to find the file. The absolute file path in Windows starts from the dirve name , for example you can copy Numbers.txt to C: empmyhomework and input the file name as:
“C:\temp\myhomework\Numbers.txt”. Note: you need to use double “”.
DiceSimulation:
/**
This class simulates rolling a pair of dice 10,000 times and
counts the number of times doubles of are rolled for each different
pair of doubles.
*/
import java.util.Random; //to use the random number generator
public class DiceSimulation
{
public static void main(String[] args)
{
final int NUMBER = 10000; //the number of times to roll the dice
//a random number generator used in simulating rolling a dice
Random generator = new Random();
int die1Value; // number of spots on the first die
int die2Value; // number of spots on the second die
int count = 0; // number of times the dice were rolled
int snakeEyes = 0; // number of times snake eyes is rolled
int twos = 0; // number of times double two is rolled
int threes = 0; // number of times double three is rolled
int fours = 0; // number of times double four is rolled
int fives = 0; // number of times double five is rolled
int sixes = 0; // number of times double six is rolled
//ENTER YOUR CODE FOR THE ALGORITHM HERE
while(count < NUMBER)
{
die1Value = generator.nextInt(6) + 1; //returns 1,2,3,4,5,or 6
die2Value = generator.nextInt(6) + 1; //returns 1,2,3,4,5,or 6
if(die1Value == die2Value)
{
if (die1Value == 1)
snakeEyes++;
else if (die1Value == 2)
twos++;
// Task #1 step 3: To do - code for die1Value = 3, 4, 5, and 6
}
count++;
}
System.out.println ("You rolled snake eyes " + snakeEyes +
" out of " + count + " rolls.");
System.out.println ("You rolled double twos " + twos +
" out of " + count + " rolls.");
System.out.println ("You rolled double threes " + threes +
" out of " + count + " rolls.");
System.out.println ("You rolled double fours " + fours +
" out of " + count + " rolls.");
System.out.println ("You rolled double fives " + fives +
" out of " + count + " rolls.");
System.out.println ("You rolled double sixes " + sixes +
" out of " + count + " rolls.");
}
}
StatsDemo:
import java.text.DecimalFormat; //for number formatting
import java.util.Scanner; //for keyboard input
import java.io.*; // for file input and output
public class StatsDemo
{
public static void main(String [] args) throws IOException //ADD A THROWS CLAUSE HERE - 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 of the numbers
String line; //a line from the file
double difference; //difference between the value and the mean
//create an object of type Decimal Format
DecimalFormat threeDecimals = new DecimalFormat("0.000");
//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: "); // user should enter Numbers.txt
filename = keyboard.nextLine();
// Create a file reader
FileReader freader = new FileReader(filename);
//Create a BufferedReader object passing it the FileReader object.
BufferedReader input = new BufferedReader(freader);
// read the first line of the file
line = input.readLine();
//loop that continues until you are at the end of the file
while (line != null)
{
//convert the line into a double value and add the value to the sum
sum += Double.parseDouble(line);
//increment the counter
count++;
//read a new line from the file
line = input.readLine();
}
//close the input file
input.close();
// Task #2 step 5: To do - calculate mean
// mean = sum/count;
//create an object of type FileWriter using “Results.txt”
FileWriter fwriter = new FileWriter("Results.txt");
//create an object of PrintWriter passing it the FileWriter object.
PrintWriter output = new PrintWriter(fwriter);
//print the results to the output file
output.println("mean = " + threeDecimals.format(mean));
//close the output file
output.close();
}
}
--------------------------------------------------------------------------
SQ004 720V05 (C:) temp JavaApplication2 organize Open Views Burn Name Favorite Links build Documents nbproject Pictures Src Music applet policy More build.xml manifest.mf Folders Numbers txt Results,txt Application? Java build Classes avaapplication2 nbproject Src JavaScript Oracle spring workFD workspace TOSAPINS Search Date modified Type 7/28/2012 2:25 PM File Folder 4/21/2012 7:33 AM File Folder 9/20/2012 6:19 PM File Folder 4/21/2012 7:33 AM POLICY File 4/10/2012 8:15 PM ML Document 4/10/2012 8:15 PM MIF File 8/22/2005 6:10 AM Text Document 9/20/2012 6:25 PM Text Document Size 1 K 4 KB 1 K 20 KB 1 KBExplanation / Answer
Below is your program: -
Task 1: - I have implemented both for loop and do while loop in same java file and commented that. We can comment and uncomment the code which we want to run. eg. if you want to run the code using for loop, comment the code with while loop and do while loop and uncomment the code with for loop, it will work.
DiceSimulation.java
/**
This class simulates rolling a pair of dice 10,000 times and
counts the number of times doubles of are rolled for each different
pair of doubles.
*/
import java.util.Random; //to use the random number generator
public class DiceSimulation {
public static void main(String[] args) {
final int NUMBER = 10000; // the number of times to roll the dice
// a random number generator used in simulating rolling a dice
Random generator = new Random();
int die1Value; // number of spots on the first die
int die2Value; // number of spots on the second die
int count = 0; // number of times the dice were rolled
int snakeEyes = 0; // number of times snake eyes is rolled
int twos = 0; // number of times double two is rolled
int threes = 0; // number of times double three is rolled
int fours = 0; // number of times double four is rolled
int fives = 0; // number of times double five is rolled
int sixes = 0; // number of times double six is rolled
// ENTER YOUR CODE FOR THE ALGORITHM HERE
while (count < NUMBER) {
die1Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
die2Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
if (die1Value == die2Value) {
if (die1Value == 1)
snakeEyes++;
else if (die1Value == 2)
twos++;
// Task #1 step 3: To do - code for die1Value = 3, 4, 5, and 6
else if (die1Value == 3)
threes++;
else if (die1Value == 4)
fours++;
else if (die1Value == 5)
fives++;
else if (die1Value == 6)
sixes++;
}
count++;
}
// With Do-While loop
// do {
// die1Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
// die2Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
// if (die1Value == die2Value) {
// if (die1Value == 1)
// snakeEyes++;
// else if (die1Value == 2)
// twos++;
// // Task #1 step 3: To do - code for die1Value = 3, 4, 5, and 6
// else if (die1Value == 3)
// threes++;
// else if (die1Value == 4)
// fours++;
// else if (die1Value == 5)
// fives++;
// else if (die1Value == 6)
// sixes++;
// }
// count++;
// } while (count < NUMBER);
// with For loop
// for (count = 0; count < NUMBER; count++) {
// die1Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
// die2Value = generator.nextInt(6) + 1; // returns 1,2,3,4,5,or 6
// if (die1Value == die2Value) {
// if (die1Value == 1)
// snakeEyes++;
// else if (die1Value == 2)
// twos++;
// // Task #1 step 3: To do - code for die1Value = 3, 4, 5, and 6
// else if (die1Value == 3)
// threes++;
// else if (die1Value == 4)
// fours++;
// else if (die1Value == 5)
// fives++;
// else if (die1Value == 6)
// sixes++;
// }
// }
System.out.println("You rolled snake eyes " + snakeEyes + " out of " + count + " rolls.");
System.out.println("You rolled double twos " + twos + " out of " + count + " rolls.");
System.out.println("You rolled double threes " + threes + " out of " + count + " rolls.");
System.out.println("You rolled double fours " + fours + " out of " + count + " rolls.");
System.out.println("You rolled double fives " + fives + " out of " + count + " rolls.");
System.out.println("You rolled double sixes " + sixes + " out of " + count + " rolls.");
}
}
Sample Run: -
// While loop: -
You rolled snake eyes 272 out of 10000 rolls.
You rolled double twos 277 out of 10000 rolls.
You rolled double threes 295 out of 10000 rolls.
You rolled double fours 266 out of 10000 rolls.
You rolled double fives 251 out of 10000 rolls.
You rolled double sixes 310 out of 10000 rolls.
//Do while loop
You rolled snake eyes 272 out of 10000 rolls.
You rolled double twos 267 out of 10000 rolls.
You rolled double threes 252 out of 10000 rolls.
You rolled double fours 275 out of 10000 rolls.
You rolled double fives 281 out of 10000 rolls.
You rolled double sixes 298 out of 10000 rolls.
//for loop
You rolled snake eyes 272 out of 10000 rolls.
You rolled double twos 229 out of 10000 rolls.
You rolled double threes 250 out of 10000 rolls.
You rolled double fours 280 out of 10000 rolls.
You rolled double fives 311 out of 10000 rolls.
You rolled double sixes 287 out of 10000 rolls.
Task 2
Numbers.txt was not there, So I created my own: -
Numbers.txt
5
6
23
5
6
8
4
7
98
6
8
1
StatsDemo.java
import java.text.DecimalFormat; //for number formatting
import java.util.Scanner; //for keyboard input
import java.io.*; // for file input and output
public class StatsDemo {
public static void main(String[] args) throws IOException // ADD A THROWS
// CLAUSE HERE -
// 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 of the numbers
String line; // a line from the file
double difference; // difference between the value and the mean
// create an object of type Decimal Format
DecimalFormat threeDecimals = new DecimalFormat("0.000");
// 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: "); // user should enter
// Numbers.txt
filename = keyboard.nextLine();
// Create a file reader
FileReader freader = new FileReader(filename);
// Create a BufferedReader object passing it the FileReader object.
BufferedReader input = new BufferedReader(freader);
// read the first line of the file
line = input.readLine();
// loop that continues until you are at the end of the file
while (line != null) {
// convert the line into a double value and add the value to the sum
sum += Double.parseDouble(line);
// increment the counter
count++;
// read a new line from the file
line = input.readLine();
}
// close the input file
input.close();
// Task #2 step 5: To do - calculate mean
mean = sum/count;
// create an object of type FileWriter using “Results.txt”
FileWriter fwriter = new FileWriter("Results.txt");
// create an object of PrintWriter passing it the FileWriter object.
PrintWriter output = new PrintWriter(fwriter);
// print the results to the output file
output.println("mean = " + threeDecimals.format(mean));
// close the output file
output.close();
}
}
Results.txt
mean = 14.750
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