How to set the file permission in Java

In Java, file permissions are very OS specific: *nix , NTFS (windows) and FAT/FAT32, all have different kind of file permissions. Java comes with some generic file permission to deal with it.

Check if the file permission allow :

1. file.canExecute(); – return true, file is executable; false is not.
2. file.canWrite(); – return true, file is writable; false is not.
3. file.canRead(); – return true, file is readable; false is not.

Set the file permission :

1. file.setExecutable(boolean); – true, allow execute operations; false to disallow it.
2. file.setReadable(boolean); – true, allow read operations; false to disallow it.
3. file.setWritable(boolean); – true, allow write operations; false to disallow it.

In *nix system, you may need to configure more specifies about file permission, e.g set a 777 permission for a file or directory, however, Java IO classes do not have ready method for it, but you can use the following dirty workaround :

Runtime.getRuntime().exec("chmod 777 file");

File permission example

FilePermissionExample.java

package com.favtuts.io.file;

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

public class FilePermissionExample {
    public static void main(String[] args) {
        try {
            File file = new File("/home/tvt/workspace/favtuts/shellscript.sh");

            if (file.exists()) {
                System.out.println("Is Execute allow : " + file.canExecute());
                System.out.println("Is Write allow : " + file.canWrite());
                System.out.println("Is Read allow : " + file.canRead());
            }

            file.setExecutable(true);
            file.setReadable(false);
            file.setWritable(false);

            System.out.println("Is Execute allow : " + file.canExecute());
            System.out.println("Is Write allow : " + file.canWrite());
            System.out.println("Is Read allow : " + file.canRead());

            if (file.createNewFile()) {
                System.out.println("File is created!");
            } else {
                System.out.println("File already exists.");
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Is Execute allow : false
Is Write allow : true
Is Read allow : true
Is Execute allow : true
Is Write allow : false
Is Read allow : false
File already exists.

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-io/file

Reference

1. http://java.sun.com/javase/6/docs/api/java/io/File.html