java.io.File#toPath() on Windows doesn't understand "NUL:" (null device)?

[David Holmes]

https://bugs.openjdk.java.net/browse/JDK-8022671

Cheers,
David

On 17/03/2021 1:21 pm, Jaikiran Pai wrote:
> Please consider this trivial code:
> 
> import java.io.*;
> import java.nio.file.*;
> 
> public class FileTest {
>      public static void main(final String[] args) throws Exception {
>          System.getProperties().list(System.out);
>          final File f = new File("NUL:");
>          try (final InputStream fis = Files.newInputStream(f.toPath())) {
>                  int numBytes = 0;
>                  while (fis.read() != -1) {
>                      System.out.println("Files.newInputStream - Read a 
> byte from " + f);
>                      numBytes++;
>                  }
>                  System.out.println("Files.newInputStream - Done reading 
> " + numBytes + " bytes from " + f);
>          }
>      }
> }
> 
> 
> The code tries to read from NUL: on a Windows setup. This code runs into 
> the following exception on Windows when the java.io.File#toPath() gets 
> invoked:
> 
> 
> Exception in thread "main" java.nio.file.InvalidPathException: Illegal 
> char <:> at index 3: NUL:
>      at 
> java.base/sun.nio.fs.WindowsPathParser.normalize(WindowsPathParser.java:182) 
> 
>      at 
> java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:153)
>      at 
> java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:77)
>      at java.base/sun.nio.fs.WindowsPath.parse(WindowsPath.java:92)
>      at 
> java.base/sun.nio.fs.WindowsFileSystem.getPath(WindowsFileSystem.java:230)
>      at java.base/java.io.File.toPath(File.java:2316)
>      at FileTest.main(FileTest.java:18)
> 
> 
> So it looks like java.io.File.toPath() on Windows isn't able to 
> recognize the null device construct?
> 
> Just to make sure this issue resides only this specific API 
> implementation, I switched the above code to use new FileInputStream(f) 
> as follows and that works as expected - reads 0 bytes and completes 
> successfully. So the NUL: construct is indeed understood by the other APIs.
> 
> 
> public class FileTest {
>      public static void main(final String[] args) throws Exception {
>          System.getProperties().list(System.out);
>          final File f = new File("NUL:");
>          try (final FileInputStream fis = new FileInputStream(f)) {
>                  int numBytes = 0;
>                  while (fis.read() != -1) {
>                      System.out.println("FileInputStream() - Read a byte 
> from " + f);
>                      numBytes++;
>                  }
>                  System.out.println("FileInputStream() - Done reading " 
> + numBytes + " bytes from " + f);
>          }
>      }
> }
> 
> Output:
> 
> FileInputStream() - Done reading 0 bytes from NUL:
> 
> Test results are from latest Java 16 release on a Windows setup.
> 
> -Jaikiran
>