Ivor Horton's Beginning Java™ 2, JDK™ 5th Edition

9.4. Exercises

You can download the source code for the examples in the book and the solutions to the following exercises from http://www.wrox.com.

1. Modify the example that avoids overwriting a file to permit the file path to be entered as a command-line argument and to allow for file names that do not have extensions.

2. File names on many systems are not of unlimited length, so appending _old to file names may break down at some point. Modify the example that avoids overwriting a file to append a three-digit numerical value to the file name to differentiate it from the existing file instead of just adding _old. The program should check for the presence of three digits at the end of the name for the existing file and replace this with a value incremented by an amount to make it unique. (That is, increment the last three digits by 1 until a unique file name is created.)

3. Write a program that will list all the directories in a directory defined by a path supplied as a command-line argument, or all the directories on a system if no command-line argument is present. (Hint: The listRoots() method will give you the roots on a system and the listFiles() method will give you an array of File objects for the files and directories in any given directory—including a root.)