avoidoverwritingfile.java

Beginning Java 2, SDK 1.4 Edition Exercise Code samples for this book

// Chapter 9 Exercise 1

// To make it more sensible I added provision for the filepath to be a command line argument.
// *** indicates modified or added code

import java.io.File;
import java.io.FileOutputStream;
 

import java.io.FileNotFoundException;

public class AvoidOverwritingFile {
  public static void main(String[] args) {
    String filepath = "C:/Beg Java Stuff/myFile.txt";

    if(args.length>0)                            // ***
      filepath = args[0];                        // ***
      
    File aFile = new File(filepath);
    FileOutputStream outputFile = null;          // Stores the stream reference
    if (aFile.isFile()) {
      File newFile = aFile;                      // Start with the original file

      // We will append "_old" to the file
      // name repeatedly until it is unique
      do {
        String name = newFile.getName();         // Get the name of the file
        int period =  name.indexOf('.');         // Find the separator for the extension
        if(period == -1)                         // ***
          newFile = new File(newFile.getParent(), name + "_old");                       // ***
        else                                                                            // ***        
          newFile = new File(newFile.getParent(), 
                           name.substring(0, period) + "_old" 
                           + name.substring(period));
      } while (!aFile.renameTo(newFile));   // Stop when renaming works
    } 

    // Now we can create the new file
    try {

      // Create the stream opened to append data
      outputFile = new FileOutputStream(aFile);
      System.out.println(aFile.getName()+" output stream created");
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    } 
    System.exit(0);
  }
}