About Question enthuware.ocpjp.v8.2.1538 :

[lveto15]

The third options has a bit misleading explanation:

WRITE will cause an exception to be thrown if the file does not exists. It will not get rid of the existing content either.

I have tested this option, and if there is empty file then the first run will fill it with data. The second run repaces this data with the new one, e.g.:
after the first run

Testing...2015-10-21T10:00:48.259

after the second run

Testing...2015-10-21T10:05:10.106

Still only one line - so the previous content has been replaced.

[admin]

Not sure how you tested but it throws a java.nio.file.FileAlreadyExistsException when the file already exists, which is what the explanation says as well.
Paul.

[lveto15]

Hm, it throws an exception if file does not exist. Maybe we are talking about different part?

I mean the second part of the explanation:

It will not get rid of the existing content either.

The procedure to test it was as following:
1. empty file optionTest.txt was created manually
2. class was run, as result content as described was in the file
3. class was run second time. The content was changed to the new one. Previous was rid off.

Below code of the class

Code: Select all

public static void main(String... args){
		writeToFile(Paths.get("optionTest.txt"), new OpenOption[]{StandardOpenOption.WRITE});
}
	
private static void writeToFile(Path path, OpenOption[] options){
		System.out.println("try with options: "+Arrays.toString(options));
		try(
			BufferedWriter br = Files.newBufferedWriter(path, Charset.forName("UTF-8"), options);		
			 ){
			br.write("Testing..."+LocalDateTime.now());
		} catch (Exception e){
			System.out.println(e);
		}	
	}	

I checked it again, this time put "One" as the initial content. After runing the content is "Testing...2015-10-21T15:13:26.518".

[admin]

Sorry, I was looking at option 4.

Regarding option 3, the part of the explanation that you've quoted is correct as well. The code given in this option will overwrite the existing content. For example, if the file had 10 bytes and if you write 1 byte using this code, only the first byte will be replaced. The rest of the 9 bytes will not be removed. The problem statement clearly says, "(the content of the existing file, if any, should go away)". This option will not do that.

HTH,
Paul.

[lveto15]

Inadequate test data = incorrect conclusion .

Thank you for the detailed explanation.

[javalass]

The default behaviour is CREATE, TRUNCATE_EXISTING, and WRITE.

When I tested it, options 1, 3 and 5 all worked as expected (i.e. truncated the text on an existing file).

[admin]

I tried it just now with option 1 an 3, they did not truncate existing file. I used the same code given in the explanation.
Can you please post the code that you tested?

-Paul.

[javalass]

Oops, you're right, they don't truncate. I too used bad examples for my text files, so I couldn't see that it was overwriting. Testing it again with a target file full of data, I can see that 1 and 3 clearly don't truncate.

Sorry about that!

[javalass]

The default of CREATE, TRUNCATE_EXISTING, and WRITE only applies if you pass no OpenOptions to the method.

[asyzdykov]

Path myfile = Paths.get("c:\\temp\\test.txt");
BufferedWriter br = Files.newBufferedWriter(myfile, Charset.forName("UTF-8"),
new OpenOption[] {StandardOpenOption.CREATE});

first option

replaces the content or create new file if not exist...
is it platform dependent behaviour?

[admin]

StandardOpenOption.CREATE only creates a new file if a file does not exit. This is not platform specific.