Create a read-only file

Question

I was wondering wether it is possible to create or simulate a file with a content set at creation and the assurance that nobody can ever change the file. If possible, can I

Answer 1

To make it so setWritable(true) does not enable writing again you could extend File and override the setWritable() methods.

import java.io.File;
import java.io.IOException;
import java.lang.Override;

public class FileAttributeDemo2 {
    private static class ReadOnlyFile extends File {
        public ReadOnlyFile(String pathname) {
            super(pathname);
        }

        @Override
        public boolean setWritable(boolean writeable) {
            return setWritable(writeable, true);
        }

        @Override
        public boolean setWritable(boolean writeable, boolean ownerOnly) {
            if (!writeable) {
                return super.setWritable(false, ownerOnly);
            }
            return false;
        }
    }

    public static void main (String[] args) throws IOException {
        File file = new ReadOnlyFile("test.txt");
        if (file.exists()) {
            file.delete();
        }
        file.createNewFile();
        System.out.println("Before. canWrite? " + file.canWrite());

        file.setWritable(false);
        System.out.println("Set writable false. canWrite? " + file.canWrite());

        file.setWritable(true);
        System.out.println("Set writable true. canWrite? " + file.canWrite());

    }
}

which produces the output:

Before. canWrite? true 
Set Writable False. canWrite? false 
Set Writable True. canWrite? false