Thread: Copying a File

Hi guys it's my first time here, I hope you guys can help me out with my question.

I'm to write a program that copies a file, I've already done that it works at copying but what I need help with is the professor wants to be able to do this from the command line:

java FileCopy sourceFileName.txt to destinationFileName.txt

How do i get my program to respond to such command from command prompt?
This is my code it copies the file when it's run from Eclipse,

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
 
public class FileCopy
{
	String srcFileName;
	String dstFileName;
	String line;
	BufferedReader source;
	PrintWriter destination;
	File fileSource;
	File destinationFile;
 
	public FileCopy(String src, String dest)
	{
		this.srcFileName = src;
		this.dstFileName = dest;
		fileSource = new File(this.srcFileName);
		destinationFile = new File(this.dstFileName);
		try 
		{
			this.copyFile();
		} 
		catch (IOException e) 
		{
			e.printStackTrace();
		}
	}
 
	private boolean openFile()
	{
		try 
		{
			if (fileSource.exists())
			{
				source = new BufferedReader(new FileReader(fileSource));
				return true;
			}
		}
		catch (FileNotFoundException e) 
		{
			e.getMessage();
		}
		return false;
	}
 
	private boolean copyFile() throws IOException
	{
		if (this.openFile() == true)
		{
			try 
			{
				destination = new PrintWriter(destinationFile);
 
				do 
				{
					line = source.readLine();
					if (line != null) 
					{
						destination.write(line + "\n");
					}
				}
 
				while (line != null);
				source.close();
				destination.close();
				return true;
			} 
			catch (FileNotFoundException e) 
			{
				e.getMessage();
			}
		}
		return false;
	}
 
	public static void main (String[] args)
	{
		FileCopy newCopy = new FileCopy("sourceFile.txt", "destinationFile.txt");
	}
 
}

This may not be the right section but I didn't know where else to post it can someone help me out please I really want to figure this out.

Try this URL for correcting the error...Jus give the source and destination file location correctly.
https://www.blogger.com/blogger.g?bl...50094219100570

Originally Posted by ubiByte

...

java FileCopy sourceFileName.txt to destinationFileName.txt

See the section of Java tutorials for Command-line Arguments

Try the following to test it:

public class Z {
    public static void main(String [] args) {
        System.out.println("Number of arguments = " + args.length);
        for (int i = 0; i < args.length; i++) {
            System.out.println("args[" + i + "] = " + args[i]);
        }
    }
}

Here are a couple of runs. (Computer output is blue, my input is black)

$ java Z
Number of arguments = 0


And

$ java Z The quality of mercy is not strained
Number of arguments = 7
args[0] = The
args[1] = quality
args[2] = of
args[3] = mercy
args[4] = is
args[5] = not
args[6] = strained



So, get the file names from the args[] array that is built by the command line.


Cheers!

Z

Originally Posted by Zaphod_b

See the section of Java tutorials for Command-line Arguments

Try the following to test it:

public class Z {
    public static void main(String [] args) {
        System.out.println("Number of arguments = " + args.length);
        for (int i = 0; i < args.length; i++) {
            System.out.println("args[" + i + "] = " + args[i]);
        }
    }
}

Here are a couple of runs. (Computer output is blue, my input is black)

$ java Z
Number of arguments = 0


And

$ java Z The quality of mercy is not strained
Number of arguments = 7
args[0] = The
args[1] = quality
args[2] = of
args[3] = mercy
args[4] = is
args[5] = not
args[6] = strained



So, get the file names from the args[] array that is built by the command line.


Cheers!

Z

Hmm so the code I have provided how can I put srcFileName into args[0] for example without creating a constructor. Because if i create a constructor it has already copied the file.

Did you read the tutorial reference that I gave? Explains about how use the args array to read Strings from the command line?

Your constructor takes two arguments. Instead of hard-coding the file names in main(), test to see that args.length is equal to 2. If it is, then use the value of args[0] and args[1] as arguments to the constructor.


Cheers!

Z

Yea I am looking through the reference I tried to code you sent me also and when I type in the same code you typed in the command prompt it says couldn't find the main class do you know why that's happening?

public static void main(String[] args) throws Exception
{
BufferedReader reader = new BufferedReader(new FileReader(args[0]));
BufferedWriter writer = new BufferedWriter(new PrintWriter(args[1]));

int index;
do
{
index = reader.read();
if (index != -1)
{
writer.write((char) index);
}
}
while (index != -1);
reader.close();
writer.close();
}

this works when i do java FileCopy input.txt out.txt, how can I put in the word "to" in between so the command reads:
java FileCopy input.txt to out.txt?