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Size of files in Java

12 replies on 1 page. Most recent reply: Apr 9, 2008 2:36 PM by Jamie Smith

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Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Size of files in Java

Posted: Apr 6, 2008 4:09 AM

Just a trivial question but I am very new to Java.

I have the following class:

public class DiskUsage
{

public static void main(String[] args)
{

if (args.length == 1)
{
FileUtilities.diskUsage(args[0]);
}
else
{
System.out.println("This is not a directory or there is not a directory in this location.");
}

/* set type */ size = FileUtilities.diskUsage(args[0]);
System.out.println("The total size of " + args[0] + " is " + size);
}
}

How do I output the size of the files in total? Where it says /* set type */ I have changed that to int but it says incompatible types.

I have another class but I don't think that is relevant to this problem.

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Size of files in Java

Posted: Apr 7, 2008 6:48 AM

In the definition of FileUtilities.diskUsage() it will say what type it returns. That is the type you should use.

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 7, 2008 7:20 AM

This is the FileUtilities class:

import java.io.*;
import java.util.*;
import java.io.File;

public class FileUtilities
{
public static void diskUsage(File f)
{

if (f.isDirectory())
{
File[] fileList = f.listFiles();

for (int i = 0; i < fileList.length; ++i)
{
diskUsage(fileList);
}
}
else
{
System.out.println(f);
}
}

public static void diskUsage(String s)
{
diskUsage(new File(s));
}
}

I have tried setting the type to int and File but they are incompatible. :s

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Size of files in Java

Posted: Apr 7, 2008 8:05 AM

Oh, you’re being taught recursion; marvellous.

Your diskUsage() doesn’t find the size of any files (hint: java.io.File has a length() method — which type does it return?); doesn’t keep a running total of disk space used; doesn’t attempt to return any answer to its caller. You need to fix all these things.

Oh, and next time you post code here, post it in java tags; that way it will display properly. http://www.artima.com/forums/howtopost.html

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 7, 2008 8:54 AM

so I need to set size to be the length of args[0]?

args[0].length ?

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Size of files in Java

Posted: Apr 7, 2008 9:33 AM

Is args[0] a java.io.File?

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 7, 2008 10:49 AM

No it isn't...that's just the arguments passed to the command line isn't it...

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Size of files in Java

Posted: Apr 7, 2008 10:55 AM

But you do have an object of type File, to which you can apply the .length() method.

I’m really not going to spell everything out for you. You have to think for yourself if you are gong to learn.

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 7, 2008 12:03 PM

fileList is of File[] type.

so...

fileList.length = FileUtilities.diskUsage ...

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 9, 2008 2:20 AM

doesn't work...

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Size of files in Java

Posted: Apr 9, 2008 7:33 AM

fileList is of type File[], not of type File. Hint: Where do you get fileList from?

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 9, 2008 10:57 AM

Ohh my bad, was looking at the wrong thing.

File f is of type file.

fileList comes from FileUtilities class

Jamie Smith

Posts: 8
Nickname: aurora88
Registered: Apr, 2008

Re: Size of files in Java

Posted: Apr 9, 2008 2:36 PM

I've tried setting long size = f.length(); in the FileUtilities class. Also, when I run this application now, it displays every folder and file twice. :s

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