Writing to a file without overwriting or appending

问题

I am writing a program in Java where the output is written to a .txt file. Each time I run the program the file is overwritten. I do not want to use the append switch and add data to the file.

I would like to have it so a new file, with the same name, is created each time I run the program. For example, if overflow.txt is the file name, and I run the program three times, the files overflow(1).txt, overflow(2).txt, and overflow(3).txt should be made.

How can this be achieved?

回答1:

Check if the file exists, if so rename it. Using File.exists and FileUtils.moveFile

You would need to do this recursively until no conflict is found.

回答2:

Check if the file exists first. If so, modify the name.

String origName = "overflow";
String ext = ".txt";
int num = 1;
file = new File(origName + ext);
while (file.exists()) {
 num++;
 file = new File(myOrigFileName +"(" + num + ")" + ext);
}

Modify depending on actual requirements. Question is not very clear.

回答3:

"A new file with the same name" doesn't make sense in most file systems.

In your example, you've got three files with different names:

overflow(1).txt
overflow(2).txt
overflow(3).txt

The bit in brackets is still part of the name. If you want to emulate that behaviour, you'll have to:

Detect the presence of the "plain" filename (if you want to write to that if it doesn't exist)
Start counting at 1, and work out the "new" filename each time by removing the extension, adding the count in brackets, then putting the extension back
Keep counting until you find a filename which doesn't exist

回答4:

String dirPath = "./";
String fileName = dirPath + "overflow.txt";
if(new File(dirPath + fileName).exist())
{
    int counter = 0;
    while(new File(dirPath + "overflow(" + ++counter + ").txt").exist());
    fileName = "overflow(" + counter + ").txt";
}

回答5:

When you instanciate the File object, verify if it exists, if it does, just rename it by adding the braces and number, and check again.

来源：https://stackoverflow.com/questions/11055695/writing-to-a-file-without-overwriting-or-appending

标签

java

file

append

overwrite