Enum StandardOpenOption and StandardCopyOption

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1.) Enum StandardOpenOption: What is the difference between CREATE and CREATE_NEW? 2.)

import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;

Will it import only one static variable? (Till now, I've only ever seen the whole class imported in all cases.) Is it obligatory to use "static" keyword in this case?

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Lisa

Level 41

22 January 2022, 00:02

useful

static import allows you to import members of a class.. means to address these members without specifying the class they are defined in. So yes, you can do that even with members of enums and yes, if you want to address these members without using the class/ enum name, then you have to do a static import. But you can static import all members of a class if you use the wildcard *

Gellert Varga

Level 23 , Szekesfehervar, Hungary

23 January 2022, 13:09

Thank you, now it's clear!:) Maybe do you have any answers to my other question? Reading the Oracle API, unfortunately I didn't understand the difference.

Lisa

Level 41

23 January 2022, 15:51

solution

Of course ;) CREATE: if the file does not exist, it creates the file, otherwise it opens the existing, overwriting what it finds CREATE_NEW: fails, means it throws an exception if a file with that name already exist eg. (CREATE is the default, so I didn't pass it explicitly)

public class OpenOptionsDemo {
    public static void main(String[] args) throws IOException {
        Path path = Paths.get("D:\\openOptionsTest.txt");

        Files.write(path, ("CREATE: 1st write, outputFile does not yet exist\n-> file getting created or exiting opened" +
                        " and output written\n\n").getBytes());
        Files.write(path, ("CREATE: 2nd write, outputFile does exist\n-> not creating a new file, opening the existing" +
                " with write access, overwriting the existing content\n\n").getBytes());
        Files.write(path, ("CREATE: 3rd try to write, file already exists, no new file created instead existing opened\n" +
                        "-> can be easily seen when appending to the existing file\n\n").getBytes(), StandardOpenOption.APPEND);
        Files.write(path, ("CREATE_NEW: 4th try to write, file already exists, CREATE_NEW fails\n-> means instead of opening " +
                        "the existing file it throws an exception\n\n").getBytes(), StandardOpenOption.CREATE_NEW);
    }
}

Gellert Varga

Level 23 , Szekesfehervar, Hungary

23 January 2022, 20:42

OK, thanks so much! All clear:)