Re: Files & Methods
To: comp.lang.java.gui
On Oct 13, 7:05 pm, cb17...@yahoo.com wrote:
Hi, I'm a new JAVA Programmer and need some help with my homework. My
homework is a multi-part assignment.
My assignment is to modify the code to find and print the sum of the
same series from 1/2 through 1/n, where n is read in from a data
file. The file series1.dat which contains a single positive integer,
can be found in the common area of my personal K: drive. My code
that I have written is not correct. A lot of error messages occur.
The code to modify:
import java.util.Scanner;
import java.io.*;
public class Summations
{
public static void main(String[] args) throws IOException
{
int value;
int sumPart = 0;
// The first part of the text.
System.out.print("The summation of the series");
// Loop from 2 to 65536, double value each loop.
for (value = 2; value <= 65536; value = value * 2)
{
sumPart = sumPart + value;
if (value > 2)
{
System.out.print(" + ");
}
System.out.print(" 1/" + value);
}
System.out.print(" = 1/" + sumPart + " ");
// Calculate the results.
double calced = 1 / (double) sumPart;
System.out.println("(" + calced + ")");
}
}
The code that I have written to complete the assignment is:
import java.util.Scanner;
import java.io.*;
public class Summations
{
public static void main (String[] args) throws IOException
{
int n;
int value;
int sumPart = 0;
int number;
String filename;
// Create a Scanner object for keyboard input.
Scanner keyboard = new Scanner(System.in);
// Get the filename.
System.out.print("Enter the filename: ");
filename = keyboard.nextLine();
// Open the file.
FileReader freader = new FileReader(filename);
BufferedReader inputFile = new BufferedReader(freader);
// Reading data from a file.
number = inputFile.readInt();
// Loop from 2 to n, doulbe value each loop.
for (value = 2; value <= n; value = value * 2)
{
sumPart = sumPart + value;
if (value > 2)
{
System.out.print(" + ");
}
System.out.print(" 1/" + value);
}
// Print results.
outputFile.print("The summation of the series");
System.out.println(" = 1/" + sumPart + " ");
// Calculate the results
double calced = 1 / (double) sumPart;
System.out.println("(" + calced +")");
// Close the file.
inputFile.close();
}
}
I don't know what a Scanner object is, it isn't in my JDK, so I did a
work around using a BufferedReader and InputStreamReader.
Notice also that I changed the calculation of "sumPart" and added a
"finalValue" in. The calculations used in the code that you were to
modify, while workable would give you a wrong answer to the math
problem involved. For example 1/2 + 1/4 = 3/4 not 1/6, or 1/2 + 1/4 +
1/8 = 7/8 not 1/14. So I used "sumPart" to keep track of the
numerator, and "finalValue" to keep track of the denominator. You
need to find a common denominator (in this case the new denominator is
always 2x the preceeding denominator) and multiply top and bottom of
both fractions by the common denominator, then do your add. So now
1/2 + 1/4 + 1/8 = 3/4 + 1/8 = 7/8.
import java.io.*;
public class Summations
{
public static void main(String[] args) throws IOException {
int value = 0;
int sumPart = 0;
int number = 0;
int finalValue = 0;
String filename = "";
// Get the filename.
System.out.print("Enter the filename: ");
BufferedReader br = new BufferedReader(new
InputStreamReader(System.in));
filename = br.readLine();
// Open the file.
FileReader freader = new FileReader(filename);
BufferedReader inputFile = new BufferedReader(freader);
// Reading data from a file.
try {
number = Integer.parseInt(inputFile.readLine());
}
catch (IOException ex) {
System.out.println("There was a problem reading the file.");
return;
}
catch (NumberFormatException ex) {
System.out.println("Could not convert file contents to a
number.");
return;
}
finally {
// Close the file.
inputFile.close();
}
// Loop from 2 to n, doulbe value each loop.
// Print results.
System.out.print("The summation of the series ");
for (value = 2; value <= number; value *= 2) {
sumPart = sumPart * 2 + 1;
if (value > 2) {
System.out.print(" + ");
}
System.out.print(" 1/" + value);
finalValue = value;
}
System.out.println(" = " + sumPart + "/" + finalValue + " ");
// Calculate the results
double calced = (double)(sumPart) / (double) finalValue;
System.out.println("(" + calced + ")");
}
}
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