Renaming files in a directory

#1
Guest_anand.sundaramurthy_*

Posted 16 May 2007 - 12:46 AM

Guests

Hi All,
Am trying to rename all the files in a given directory,for ex if theres a file called hello.xls,hello1.xls then after the execution of the program it must become hello_Bs.xls,hello1_Bs.xls
I have written a simple code for this but am getting null pointer exception.
can anybody pls temme wats worng with the code.

import java.io.*;
import java.lang.*;
import java.util.*;

public class Ls {
	public static void main(String args[]) 
	{
		String[] dir = new java.io.File("c:\\Documents and Settings\\Admin\\Desktop\\New Folder").list();
		java.util.Arrays.sort(dir); 
		File f[] = new File("c:\\Documents and Settings\\Admin\\Desktop\\New Folder)").listFiles();
		int len1 = dir.length;
		for (int i=0;i<len1; i++)
		{
			System.out.println(dir[i]);
			String name = f[i].getName();
			System.out.println(name);
			int j=name.indexOf('.');
			System.out.println(j);
			String newname = name.substring(0,j-1) + "_BS" + name.substring(j+1,name.length());	
			System.out.println(newname);
			File newFileName=new File(f[i].getParentFile(), newname);
			System.out.println("newFileName="+newFileName);
			f[i].renameTo(newFileName);   
		}
	}	
}

#2
John

Posted 16 May 2007 - 03:39 AM

Writes binary right handed and hex left handed

Moderators
6,321 posts

I don't have time to dig into it right now, but this is your problem:

f[i].getName()

#3
oubless

Posted 29 May 2007 - 01:01 AM

Newbie

Members
22 posts

The problem is here


String newname = name.substring(0,j-1) + "_BS" + name.substring(j+1,name.length());

substring( a, b ) means including a excluding b

Fixed:



import java.io.File;


public class Ls {

	public static void main(String args[]) 

	{

		String[] dir = new java.io.File("test").list();

		java.util.Arrays.sort(dir); 

		File f[] = new File("test").listFiles();

		int len1 = dir.length;

		for (int i=0;i<len1; i++)

		{

			System.out.println(dir[i]);

			String name = f[i].getName();

			System.out.println(name);

			int j=name.indexOf('.');

			System.out.println(j);

			String newname = name.substring(0,j) + "_BS" + name.substring(j,name.length());	

			System.out.println(newname);

			File newFileName=new File(f[i].getParentFile(), newname);

			System.out.println("newFileName="+newFileName);

			f[i].renameTo(newFileName);   

		}

	}	

}