Question

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

Answer 1

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;
   }
}

Sample Output:



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