File read-write mode in java

[ISAIAH]

Hello,
I want to create a file that would be write-only mode. But I see no solution for doing that in java. In C / C + +, it specifies the open mode in a parameter in Java I do not know how to do that. Briefly how to perform read write mode operations in java. Thank you for your help.

[Zecho]

Hello,
Is that you can show your need? I think this what you have explained is not so clear, more explanation is needed. If not, creates a temporary file and save it under any name and then I think you have to use the java.io package to perform the needed operations on write and read permission of a file.

[ISAIAH]

Hello,
I am aware that there are ways such as creating a file in another directory and rename it, but it is not very clean what. All I want is to have the equivalent of C / C + + where you can create a file access mode "a" (there is also a + r, r + w, w +). In summary, I want to create a file and not make it accessible even to read, only when I finished writing this file, i.e after I closed. How can it be achieved, is it that it is not possible in java. Thanks for your answers.

[Praetor]

Hi,

All I want is to have the equivalent of C / C + + where you can create a file access mode "a" (there is also a + r, r + w, w +).

If I am not mistaken you speak of fopen () function which is used in C.

has : Opens the file for writing. The file is created if it did not exist. The stream is positioned at the end of the file.

So "a" stands for write access with the append at the end of the file, and that is what fair FileOutputStream when you use the constructor with parameter append to true.

In summary, I want to create a file and not make it accessible even to read, only when I finished writing this file, ie after I closed.

Accessible to whom? For other programs, know that the "a" of fopen () does not block read access to the file from other applications. If still it is what you want to do it you must use the FileLock obtained from FileChannel for your OuputStream:

FileOutputStream fout = new FileOutputStream(filename, true);
FileLock lock = fout.getChannel().lock();
try {
 
	/ / Write file
 
 
} finally {
	lock.release();
}

But the lock depends on the operating system and can vary from one platform to another.

[ISAIAH]

Hi,
I speak of fopen. Indeed, the "a" describes what you said, but the description of "a +" says it also opens the file for reading, suggesting that the "a" file was not so much playback mode. But in fact, seems FileLock do what I want. And I do not understand why it is platform-dependent. Finally I say that but I doubt it's got to be a valid reason, at least I hope. The safest way seems to be good to go through a temporary file and rename it, I think it's a shame but good. Why is it not an access mode describing each situation: R, R / W, W, Read-only; Read-only/Write; Write-only, etc. .... ?

[opaper]

Hello,
The philosophy of Java is different from that of C. This is something that must be understood before attempting to do anything. In Java, we use the concept of data flows for input-output. Inflow or outflow, which may be the keyboard, screen, file, the output of a servlet, a buffer, the exit where the standard input in Unix, etc. It is an advantage. You can easily schedule a method that takes a stream parameter. No matter if this flow then gives the output of a servlet, a buffer memory, or file. It's something I have been very useful for generating pdf documents in several contexts. Knowing this, write to the end of a file is to write out a stream that points to a file. So use the class FileOutputStream. The class FileLock avoids access concurrent. The API of these classes will give you all the details.