FULL PRODUCT VERSION :
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux hostname 3.2.0-4-amd64 #1 SMP Debian 3.2.65-1+deb7u1 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Calling toUri() on a Path obtained from a FileSystem created with the Zip File System Provider returns a URI which has been percent-encoded twice. This is easily observed by creating a zip file system from a path containing one or more spaces: The URI obtained from an entry's path will contain "%2520" for each space.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Pass a "jar:" URI containing one or more percent escapes (such as a file: URI corresponding to a Path with one or more spaces) to FileSystems.newFileSystem. For any existing Path in the returned FileSystem, call Path.toUri() and observe the returned value.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The returned URI should be a valid, readable URI, regardless of whether the URI of the zip archive contains any percent-escapes.
ACTUAL -
Calling Path.toUri() returns a URI in which the "%" of each escaped octet has itself been encoded as "%25".

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.util.Map;
import java.util.Collections;
import java.net.URI;
import java.io.IOException;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;

public class JarPathTest {
    public static void main(String[] args)
    throws IOException {

        Path zip = Paths.get(args[0]);

        URI zipURI = URI.create("jar:" + zip.toUri());
        System.out.println(zipURI);

        Map<String, String> env = Collections.emptyMap();

        try (FileSystem fs = FileSystems.newFileSystem(zipURI, env)) {
            Path root = fs.getPath("/");
            URI uri = root.toUri();
            System.out.println(uri);

            Paths.get(uri);
        }
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Treat the URI's decoded parts as if they are percent-encoded:

        uri = URI.create(
            uri.getScheme() + ":" + uri.getSchemeSpecificPart());