Creating a temporary directory in jdk 6 vs jdk 8

Question

I'am facing a weird issue in our dev domains . So basically our java app currently runs on jdk1.6 , we are planning to upgrade that to 1.8 . So currently the following code works fine in 1.6 but returns an exception

java.io.IOException: Unable to create temporary file, C:\Users\xxxxx\xxxxx\Local\Temp\XYZDirectory at java.io.File$TempDirectory.generateFile(File.java:1921) at java.io.File.createTempFile(File.java:2010) at java.io.File.createTempFile(File.java:2070)

in 1.8 . Code is as follows -

File file = null;
    try {
        file =
            File.createTempFile("XYZ", "Directory" + System.getProperty("file.separator"));
        file.delete();
        file.mkdirs();
    } catch (final IOException e) {
        e.printStackTrace();
    }
    return file;

We want our product to be compatible with both 1.6 and 1.8 .

After some research i found that i might have to use the following method of Files class

public static Path createTempDirectory(Path dir,
                   String prefix,
                   FileAttribute<?>... attrs)
                            throws IOException

So i have the following queries -

1) Why File.createTempFile throws an Exception in 1.8 ?

2) What is the conceptual difference between the two methods ?

3) More over if File.createTempFile is no longer supported why it is not deprecated ?

4) What is the suitable way to address this issue ? In other words i can do a programmatic check to use appropriate method on the basis of jdk version installed in the VM and then proceed with the creation of temporary directory , but is this best way to to address this issue ?

Java 8 doesn't like you trying to include `System.getProperty("file.separator")` as part of the suffix string. — greg-449, Mar 15 '16 at 15:24
*"Why File.createTempFile throws an Exception in 1.8 ?"* Looks like it doesn't allow that hackisch (and bad looking) way to create a temporary directory. — Tom, Mar 15 '16 at 15:25
`Files.createTempDirectory` is what you should use. Don't hack your way through. I'm even baffled that this worked in Java 6. — Tunaki, Mar 15 '16 at 15:29
Thank you everyone for taking time out of your busy schedule to look into this issue . — Learner, Mar 16 '16 at 04:45
Iam just curious why having 'System.getProperty("file.separator")' works in 1.6 and doesnt work in 1.8 . Is there any change in the code of 'createTempFile' method from 1.6 to 1.8 .Is there any release notes or documentation that conveys these changes , — Learner, Mar 18 '16 at 06:32

David S. · Accepted Answer · 2016-03-15T18:00:34.293

-3

This works on both:

        File file = null;
    try {
        file = File.createTempFile("XYZ", "Directory");
        file.delete();
        file.mkdirs();
        System.out.println(file);
    } catch (final IOException e) {
        e.printStackTrace();
    }
    return file;

I am not sure why concatenating the file separator fails, but that's the cause of the exception. My guess is that the separator is inserted programmatically by the File class and that you adding one manually causes the failure.

With that said, here is the NIO version introduced in Java 7 that is recommended:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public class TempStackTest {
    public Path getTempFilePath() {
        Path path = null;
        try {
            path = Files.createTempFile("XYZ", "Directory");
            path.toFile().delete();
        } catch (final IOException e) {
            e.printStackTrace();
        }
        return path;
    }
}

edited Mar 15 '16 at 18:00

answered Mar 15 '16 at 15:28

David S.

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2

Since the OP is migrating with Java 8, best to use current up to date API, like NIO.2 (which is actually present since Java 7 already). – Tunaki Mar 15 '16 at 15:31
5

When using NIO, use [`Files.createTempDirectory(…)`](https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#createTempDirectory-java.nio.file.Path-java.lang.String-java.nio.file.attribute.FileAttribute...-) in the first place to get rid of the “create file just to delete it afterwards” hack. And when you have to delete a file in NIO, use [`Files.delete(…)`](https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#delete-java.nio.file.Path-) to benefit from the NIO API (like learning about *why* a deletion failed) instead of falling back to crap-IO via `.toFile().delete()` – Holger Mar 15 '16 at 18:22

Creating a temporary directory in jdk 6 vs jdk 8

1 Answers1