Java Chapter 12.29 (Rename files) suppose you have a lot of files in a directory named Exercisei_j, where i and j are digits. Write a program that pads a 0 before j if j is a single digit. For example, a file named Exercise2_1 in a directory will be renamed to Exercise2_01. In Java, when you pass the symbol * from the command line, it refers to all files in the directory (see Supplement III.V). Use the following command to run your program. java Exercise12_29 * can you make a example directory with sample files.. Please type you answer. Thanks

I have this code. but I cannot seem to make it rename the files.

RenameFiles.java:

import java.io.File;

public class RenameFiles {

public static void main(String[] args) { if(args.length != 0) { for(String name: args) { File f = new File(name); if(f.isFile()){ String newName = getNewName(f.getName()); if(newName != null) { File newFile = new File(newName); f.renameTo(newFile); } } } } }

private static String getNewName(String name) { String tokens[] = name.split("_"); // if string is ending on _ without any digit at last if(name.charAt(name.length()-1) == '_') { return null; } // if string has got _ then, there will be atleast two parts if(tokens.length >= 2) { String fullName = ""; int i=0; while(i < tokens.length-1) { fullName += tokens[i] + "_"; i++; } // if last token is single digit if(tokens[tokens.length - 1].length()==1) { if(Character.isDigit(tokens[tokens.length - 1].charAt(0))) { fullName += "0" + tokens[tokens.length-1]; return fullName; } else return null; } else return null; } return null; } }

I believe the code should be Program can be run as : java RenameFiles * as shown in the above image. It changes the files names as expected.

I put the RenameFiles.java & class in the same folder in windows and the abc_1, abc_2 & abc_3. I have not been able the rename the as described. can you tell me what I am doing wrong?