File I/O Operations

[Mckenzie John]

Hi

i need to understand the file I/O operations in the following code

package com.scjp;

import java.io.File;
import java.io.IOException;

public class FileLearning {
public static void main(String[] args) throws IOException{
	File file = new File("myDir");
	file.mkdir();
	File contentFile = new File(file, "myFile");
	contentFile.createNewFile();// will this add a file of name myFile to the directory myDir?
	
	System.out.println("file is a directory"+file.isDirectory());
	System.out.println("contentFile is a file"+contentFile.isFile());
	System.out.println("Name of file before rename"+file.getName());
	File newDirName = new File("newDirName"); // assigning a new file object to rename my dir
	file.renameTo(newDirName);
	System.out.println("Name of file after rename"+file.getName()); // Why the name of the Dir  is not renamed
}
}

[Anayonkar]: Added code tags


I have added my questions against the lines as comment. Please help me understanding the concepts.

Thanks,
Mckenzie

[R. Jain]

That is happening because, when you are renaming your file to a different file object, then a new file is created, content of old file / directory is copied there, and the old file/directory is deleted.

So, after the rename operation, your directory referenced by `file` object doesn't exist.

Try using this: -

file.renameTo(newDirName);    		
if (file.exists()) {
	System.out.println("Name of file after rename : "+file.getName()); // Why the name of the Dir is not renamed	
}

[Chan Ag]

Try changing your code as follows.

System.out.println("File exists yet " + contentFile.exists());
contentFile.createNewFile();// will this add a file of name myFile to the directory myDir? 
System.out.println("File exists yet " + contentFile.exists());

and

System.out.println("Directory Rename Successful " +file.renameTo(newDirName)); 

And delete myDir and newDirName ( physical directories and files) and run this program twice and note the difference. That will answer your first and second question.

As for the last question, I think the original file/dir references are not deleted after we rename a file/directory. In any case a File object is just a file ( directory or file ) name that exists even after a rename. The old reference has a name ( file/directory name) but the actual physical dir/file as such does not exist cause it has been renamed. It is the new reference that is now mapped with the physical file/direcory after the rename. So a file or directory reference variable would still have the same name although the actual file/directory may not exist.