I have started learning Java and am having problem with a simple program that should write some content to numbers.dat file.
I am facing two problems:
-
The output that I am getting is as follows:
2, 6, 12, 20, 30, 42, 56, 72, 90, 110, 132, 156, 182, 210, 240, 272, 306, 342, 380, 420, 462, 506, 552, 600, 650, 702, 756, 812, 870, 930, 992, 1056, 1122, 1190, 1260, 1332, 1406, 1482, 1560, 1640, 1722, 1806, 1892, 1980, 2070, 2162, 2256, 2352, 2450, 2550…
When it should be:
For even numbers:
2,4,6,8,10,12,14,……,98,100
For odd numbers:
2,4,6,8,10,12,14,……,98,100,1,3,5,7,9,……..97,99
-
My second problem is that the output is not getting written to
numbers.datfile! It’s all blank.
The question from the book that I am trying to solve is:
Write a program called TextFileIO.java to create a file named numbers.dat. Then create an algorithm that writes all even numbered integers from 1 to 100, separated by a comma.
After the file has been created, close and reopen the file and display the results to the screen. After the results have been displayed append the odd number integers from 1 to 100, separated by a comma to the end of the file. Reopen the file and display the results. The contents of the file should be the even numbers from 1 to 100 separated by a comma followed by the odd number from 1 to 100 separated by a comma. The output of this program would be something like the following:
2,4,6,8,10,12,14,……,98,100
2,4,6,8,10,12,14,……,98,100,1,3,5,7,9,……..97,99
Below is the code that I have tried so far:
textFileIO.java
package package1;
import java.io.*;
import java.util.*;
//class definition
public class textFileIO{
//The main function
public static void main(String args[]) {
//This declares a file to open.
File outFile = new File("numbers.dat");
int sumEven = 0;
int sumOdd = 0;
//File IO requires a try/catch block to prevent the program from crashing
try {
//a buffered writer is used to allow us to write to the file.
BufferedWriter writer = new BufferedWriter(new FileWriter(outFile));
//This for loop handles adding all of the numbers together
for(int i = 1; i < 100; i += 2) {
sumEven += i + 1;
writer.write("" + sumEven + ", ");
}
//adding a new line and closing the file
writer.newLine();
writer.close();
//A buffered Reader is used for reading a new file.
BufferedReader reader = new BufferedReader(new FileReader(outFile));
//Because I only add a new line at the end, I only need to read the first line.
System.out.println(reader.readLine());
//I need to write again, so I close the reader and open the writer.
reader.close();
//you need to create another object to append to the file
//writer.open();
BufferedWriter writer2 = new BufferedWriter(new FileWriter(outFile));
//This for loop is identical to the previous one, except for odd numbers
for(int i = 1; i < 100; i += 2) {
sumOdd += i;
writer2.write("" + sumOdd + ", ");
}
writer.newLine();
writer.close();
//The same here. You need to create another reader
//reader.open();
BufferedReader reader2 = new BufferedReader(new FileReader(outFile));
System.out.println(reader2.readLine());
}
catch (Exception e) {
}
}
}
Edit 2
I changed my code and this is my latest code. I am still having problems.
The console output screen is showing 49 and 50 as output and my numbers.dat file is now showing only comma separated list of odd numbers. What am I doing wrong now?
import java.io.*;
import java.util.*;
public class TextFileIO {
public static void main(String[] args) throws Exception {
//Clear the contents of numbers.dat if already exists and populated
File fileOne = new File("numbers.dat");
fileOne.delete();
File newFile = new File("numbers.dat");
newFile.createNewFile();
//Create writer object
PrintWriter writer = new PrintWriter(new FileWriter("numbers.dat"));
//Loop from 1 to 100
for (int i = 1; i <= 100; i++) {
//If number is even, write to file
if (i % 2 == 0) {
writer.print(i + ",");
}
}
//Close writer object.
writer.close();
//Read from file
FileInputStream fileStream = new FileInputStream("numbers.dat");
DataInputStream in = new DataInputStream(fileStream);
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
//Print line
System.out.println(reader.read());
reader.close();
//Write all odd numbers to file
PrintWriter writer2 = new PrintWriter(new FileWriter("numbers.dat"));
//Loop from 1 to 100
for (int i = 1; i <= 100; i++) {
//If number is odd, write to file
if (i % 2 == 1) {
writer2.print(i + ",");
}
}
writer2.close();
//Read from file
FileInputStream fileStream2 = new FileInputStream("numbers.dat");
DataInputStream in2 = new DataInputStream(fileStream2);
BufferedReader reader2 = new BufferedReader(new InputStreamReader(in2));
//Print line
System.out.println(reader2.read());
reader.close();
}
}
Edit 3: I am still unable to get the desired output. I am still getting the output in console as 49 and 50, and in numbers.dat file, the output is still only odd numbers separated by commas. I am unable to understand what exactly to change in my code.
For the correct number to print you should change
Even number loop:
Odd number loop:
And replace your following statement:
with
and you should be done.
EDIT
This worked perfectly for me and here is the output…