Program to Copy data of one file into another file for 15 times

Question

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class JavaCopyFile {

    public static void main(String[] args) throws InterruptedException, IOException {


        int i=0,count=0;;
        while(i<15) {
        File source = new File("error.txt");
        File dest = new File("criteria.txt");

        // copy file conventional way using Stream
        //long start = System.nanoTime();
        copyFileUsingStream(source, dest);
        //System.out.println("Time taken by Stream Copy = " + (System.nanoTime() - start));

        if(i<15) {

            count++;
        }
        i++;
    }
        System.out.println(count);
    }
    private static void copyFileUsingStream(File source, File dest)

            throws IOException {

        InputStream input = null;

        OutputStream output = null;

        try {

            input = new FileInputStream(source);

            output = new FileOutputStream(dest);

            byte[] buf = new byte[1024];

            int bytesRead;

            while ((bytesRead = input.read(buf)) > 0) {

                output.write(buf, 0, bytesRead);

            }

        }catch(Exception e) {
            System.out.println("File not found exception");/*finally {

            input.close();

            output.close();
*/
        }

    }

}

I have written code as above - for testing purpose I set count variable. count is giving 15 it is perfect. But file is copying once only. I want to copy the file for 15 times to the same destination file. Please help me to solve this problem. I am a beginner in java programming.

Don't you need different file names if you want to copy it 15 times? Because now it is just over-writing it each time. — Nicholas K, Nov 08 '18 at 06:18
can we copy in same file.I mean both source and destination files can be same? — Naga Pavan, Nov 08 '18 at 06:20
it gives the destination file a unique file name every loop. The files will be named like `criteria0.txt`, `criteria1.txt`, ... — LonelyCpp, Nov 08 '18 at 06:28
No,I don't want like that.I want the same file name and data should be copied 15 times. — Naga Pavan, Nov 08 '18 at 06:30

Nicholas K · Accepted Answer · 2018-11-08T12:50:02.540

As suggested in the comments, your logic is correct but you are re-writing the destination file every time.

Use the variable i to denote each tiem you are writing to a new destination file as shown below :

File dest = new File("criteria" + i + ".txt");

This will create 15 files in the destination and thus avoids re-writing the same destination.

EDIT :

As per your latest comment change the code to as follows :

public static void main(String[] args) throws InterruptedException, IOException {
    int i = 0, count = 0;
    File source = new File("error.txt");
    File dest = new File("criteria.txt");
    OutputStream output = new FileOutputStream(dest);
    while (i < 15) {
        copyFileUsingStream(source, output);
        if (i < 15) {
            count++;
        }
        i++;
    }
    System.out.println(count);
}

private static void copyFileUsingStream(File source, OutputStream output) 
  throws IOException {
    InputStream input = null;
    try {
        input = new FileInputStream(source);
        byte[] buf = new byte[1024];
        int bytesRead;
        while ((bytesRead = input.read(buf)) > 0) {
            output.write(buf, 0, bytesRead);
        }
    } catch (Exception e) {
        System.out.println("File not found exception");
    }
}

Instead of creating the OutputStream in each iteration of the loop, create it once and pass it to copyFileUsingStream every time so that the previous stream is maintained.

if i wrote like that, suppose 15 times copying means 15 files,it's ok. But if i want to copy 100 times means 100 files.Is it a correct way to do it. — Naga Pavan, Nov 08 '18 at 06:33
no,I don't want to change destination file name, because i am using it in another method. — Naga Pavan, Nov 08 '18 at 06:34
Then you have to implement it copy one time, and after the `consumer method` finished reading/process the file then it will call again to start copy another file? — Dang Nguyen, Nov 08 '18 at 06:45
@NagaPavan : Made an edit as per your comment. Hope it helps. — Nicholas K, Nov 08 '18 at 06:46

Program to Copy data of one file into another file for 15 times

1 Answers1