test/jdk/java/io/File/ListRoots.java

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 *
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/* @test
   @bug 4071322
   @summary Basic test for File.listRoots method
 */

import java.io.File;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

public class ListRoots {

    public static void main(String[] args) throws Exception {
        File[] rs = File.listRoots();
        for (int i = 0; i < rs.length; i++) {
            System.out.println(i + ": " + rs[i]);
        }

        File f = new File(System.getProperty("test.src", "."), "ListRoots.java");
        String cp = f.getCanonicalPath();
        boolean found = Stream.of(rs)
                .map(File::getPath)
                .anyMatch(p -> cp.startsWith(p));
        if (!found) {
            throw new RuntimeException(cp + " does not have a recognized root");
        }

        // the list of roots should match FileSystem::getRootDirectories
        Set<File> roots1 = Stream.of(rs).collect(Collectors.toSet());
        FileSystem fs = FileSystems.getDefault();
        Set<File> roots2 = StreamSupport.stream(fs.getRootDirectories().spliterator(), false)
                .map(Path::toFile)
                .collect(Collectors.toSet());
        if (!roots1.equals(roots2)) {
            System.out.println(roots2);
            throw new RuntimeException("Does not match FileSystem::getRootDirectories");
        }
    }

}