8024695: new File("").exists() returns false whereas it is the current working directory

Reviewed-by: alanb, rriggs, lancea

src/java.base/share/classes/java/io/File.java

@@ -56,7 +56,8 @@ import jdk.internal.util.StaticProperty;
  * case of Microsoft Windows UNC pathnames, a hostname.  Each subsequent name
  * in an abstract pathname denotes a directory; the last name may denote
  * either a directory or a file.  The <em>empty</em> abstract pathname has no
- * prefix and an empty name sequence.
+ * prefix and an empty name sequence.  Accessing a file with the empty abstract
+ * pathname is equivalent to accessing the current user directory.
  *
  * <p> The conversion of a pathname string to or from an abstract pathname is
  * inherently system-dependent.  When an abstract pathname is converted into a

src/java.base/share/classes/java/io/FileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -33,6 +33,22 @@ import java.lang.annotation.Native;
 
 abstract class FileSystem {
 
+    /* -- Current Working Directory --*/
+
+    /* lazy initialization of CWD object */
+    private static class CurrentWorkingDirectoryHolder {
+        static final File CURRENT_WORKING_DIRECTORY = currentWorkingDirectory();
+
+        private static final File currentWorkingDirectory() {
+            return new File(".");
+        }
+    }
+
+    /* CWD object accessor */
+    static File getCWD() {
+        return CurrentWorkingDirectoryHolder.CURRENT_WORKING_DIRECTORY;
+    }
+
     /* -- Normalization and construction -- */
 
     /**

src/java.base/unix/classes/java/io/UnixFileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -29,11 +29,18 @@ import java.util.Properties;
 import jdk.internal.util.StaticProperty;
 
 final class UnixFileSystem extends FileSystem {
-
     private final char slash;
     private final char colon;
     private final String userDir;
 
+    private String getPathForSysCalls(String path) {
+        return path.isEmpty() ? getCWD().getPath() : path;
+    }
+
+    private File getFileForSysCalls(File file) {
+        return file.getPath().isEmpty() ? getCWD() : file;
+    }
+
     UnixFileSystem() {
         Properties props = System.getProperties();
         slash = props.getProperty("file.separator").charAt(0);
@@ -154,7 +161,7 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public String canonicalize(String path) throws IOException {
-        return canonicalize0(path);
+        return canonicalize0(getPathForSysCalls(path));
     }
     private native String canonicalize0(String path) throws IOException;
 
@@ -164,13 +171,13 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public int getBooleanAttributes(File f) {
-        int rv = getBooleanAttributes0(f);
+        int rv = getBooleanAttributes0(getFileForSysCalls(f));
         return rv | isHidden(f);
     }
 
     @Override
     public boolean hasBooleanAttributes(File f, int attributes) {
-        int rv = getBooleanAttributes0(f);
+        int rv = getBooleanAttributes0(getFileForSysCalls(f));
         if ((attributes & BA_HIDDEN) != 0) {
             rv |= isHidden(f);
         }
@@ -183,25 +190,25 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public boolean checkAccess(File f, int access) {
-        return checkAccess0(f, access);
+        return checkAccess0(getFileForSysCalls(f), access);
     }
     private native boolean checkAccess0(File f, int access);
 
     @Override
     public long getLastModifiedTime(File f) {
-        return getLastModifiedTime0(f);
+        return getLastModifiedTime0(getFileForSysCalls(f));
     }
     private native long getLastModifiedTime0(File f);
 
     @Override
     public long getLength(File f) {
-        return getLength0(f);
+        return getLength0(getFileForSysCalls(f));
     }
     private native long getLength0(File f);
 
     @Override
     public boolean setPermission(File f, int access, boolean enable, boolean owneronly) {
-        return setPermission0(f, access, enable, owneronly);
+        return setPermission0(getFileForSysCalls(f), access, enable, owneronly);
     }
     private native boolean setPermission0(File f, int access, boolean enable, boolean owneronly);
 
@@ -215,37 +222,37 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public boolean delete(File f) {
-        return delete0(f);
+        return delete0(getFileForSysCalls(f));
     }
     private native boolean delete0(File f);
 
     @Override
     public String[] list(File f) {
-        return list0(f);
+        return list0(getFileForSysCalls(f));
     }
     private native String[] list0(File f);
 
     @Override
     public boolean createDirectory(File f) {
-        return createDirectory0(f);
+        return createDirectory0(getFileForSysCalls(f));
     }
     private native boolean createDirectory0(File f);
 
     @Override
     public boolean rename(File f1, File f2) {
-        return rename0(f1, f2);
+        return rename0(getFileForSysCalls(f1), getFileForSysCalls(f2));
     }
     private native boolean rename0(File f1, File f2);
 
     @Override
     public boolean setLastModifiedTime(File f, long time) {
-        return setLastModifiedTime0(f, time);
+        return setLastModifiedTime0(getFileForSysCalls(f), time);
     }
     private native boolean setLastModifiedTime0(File f, long time);
 
     @Override
     public boolean setReadOnly(File f) {
-        return setReadOnly0(f);
+        return setReadOnly0(getFileForSysCalls(f));
     }
     private native boolean setReadOnly0(File f);
 
@@ -260,7 +267,7 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public long getSpace(File f, int t) {
-        return getSpace0(f, t);
+        return getSpace0(getFileForSysCalls(f), t);
     }
     private native long getSpace0(File f, int t);
 
@@ -270,7 +277,7 @@ final class UnixFileSystem extends FileSystem {
 
     @Override
     public int getNameMax(String path) {
-        long nameMax = getNameMax0(path);
+        long nameMax = getNameMax0(getPathForSysCalls(path));
         if (nameMax > Integer.MAX_VALUE) {
             nameMax = Integer.MAX_VALUE;
         }

src/java.base/windows/classes/java/io/WinNTFileSystem.java

@@ -79,6 +79,14 @@ final class WinNTFileSystem extends FileSystem {
         return path;
     }
 
+    private String getPathForWin32Calls(String path) {
+        return (path != null && path.isEmpty()) ? getCWD().getPath() : path;
+    }
+
+    private File getFileForWin32Calls(File file) {
+        return file.getPath().isEmpty() ? getCWD() : file;
+    }
+
     WinNTFileSystem() {
         Properties props = System.getProperties();
         slash = props.getProperty("file.separator").charAt(0);
@@ -495,31 +503,31 @@ final class WinNTFileSystem extends FileSystem {
 
     @Override
     public int getBooleanAttributes(File f) {
-        return getBooleanAttributes0(f);
+        return getBooleanAttributes0(getFileForWin32Calls(f));
     }
     private native int getBooleanAttributes0(File f);
 
     @Override
     public boolean checkAccess(File f, int access) {
-        return checkAccess0(f, access);
+        return checkAccess0(getFileForWin32Calls(f), access);
     }
     private native boolean checkAccess0(File f, int access);
 
     @Override
     public long getLastModifiedTime(File f) {
-        return getLastModifiedTime0(f);
+        return getLastModifiedTime0(getFileForWin32Calls(f));
     }
     private native long getLastModifiedTime0(File f);
 
     @Override
     public long getLength(File f) {
-        return getLength0(f);
+        return getLength0(getFileForWin32Calls(f));
     }
     private native long getLength0(File f);
 
     @Override
     public boolean setPermission(File f, int access, boolean enable, boolean owneronly) {
-        return setPermission0(f, access, enable, owneronly);
+        return setPermission0(getFileForWin32Calls(f), access, enable, owneronly);
     }
     private native boolean setPermission0(File f, int access, boolean enable, boolean owneronly);
 
@@ -533,7 +541,7 @@ final class WinNTFileSystem extends FileSystem {
 
     @Override
     public String[] list(File f) {
-        return list0(f);
+        return list0(getFileForWin32Calls(f));
     }
     private native String[] list0(File f);
 
@@ -545,7 +553,7 @@ final class WinNTFileSystem extends FileSystem {
 
     @Override
     public boolean setLastModifiedTime(File f, long time) {
-        return setLastModifiedTime0(f, time);
+        return setLastModifiedTime0(getFileForWin32Calls(f), time);
     }
     private native boolean setLastModifiedTime0(File f, long time);
 
@@ -591,7 +599,7 @@ final class WinNTFileSystem extends FileSystem {
             // that free space <= total space
             if (t == SPACE_FREE)
                 t = SPACE_USABLE;
-            return getSpace0(f, t);
+            return getSpace0(getFileForWin32Calls(f), t);
         }
         return 0;
     }
@@ -618,7 +626,7 @@ final class WinNTFileSystem extends FileSystem {
                 }
             }
         }
-        return getNameMax0(s);
+        return getNameMax0(getPathForWin32Calls(s));
     }
 
     @Override

test/jdk/java/io/File/EmptyPath.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -22,28 +22,257 @@
  */
 
 /* @test
-   @bug 4842706
-   @summary Test some file operations with empty path
+ * @bug 4842706 8024695
+ * @summary Test some file operations with empty path
+ * @run junit EmptyPath
  */
 
-import java.io.*;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.FileStore;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class EmptyPath {
-    public static void main(String [] args) throws Exception {
-        File f = new File("");
-        f.mkdir();
-        try {
-            f.createNewFile();
-            throw new RuntimeException("Expected exception not thrown");
-        } catch (IOException ioe) {
-            // Correct result
-        }
-        try {
-            FileInputStream fis = new FileInputStream(f);
-            fis.close();
-            throw new RuntimeException("Expected exception not thrown");
-        } catch (FileNotFoundException fnfe) {
-            // Correct result
+    private static final String EMPTY_STRING = "";
+
+    static File f;
+    static Path p;
+
+    @BeforeAll
+    public static void init() {
+        f = new File(EMPTY_STRING);
+        p = Path.of(EMPTY_STRING);
+    }
+
+    @Test
+    public void canExecute() {
+        assertTrue(f.canExecute());
+    }
+
+    @Test
+    public void canRead() {
+        assertTrue(f.canRead());
+    }
+
+    @Test
+    public void canWrite() {
+        assertTrue(f.canWrite());
+    }
+
+    @Test
+    public void compareTo() {
+        assertEquals(0, f.compareTo(p.toFile()));
+    }
+
+    @Test
+    public void createNewFile() {
+        assertThrows(IOException.class, () -> f.createNewFile());
+    }
+
+    @Test
+    public void open() throws FileNotFoundException {
+        assertThrows(FileNotFoundException.class,
+                     () -> new FileInputStream(f));
+    }
+
+    @Test
+    public void delete() {
+        assertFalse(f.delete());
+    }
+
+    @Test
+    public void equals() {
+        assertTrue(f.equals(p.toFile()));
+    }
+
+    @Test
+    public void exists() {
+        assertTrue(f.exists());
+    }
+
+    @Test
+    public void getAbsolutePath() {
+        System.out.println(p.toAbsolutePath().toString() + "\n" +
+                           f.getAbsolutePath());
+        assertEquals(p.toAbsolutePath().toString(), f.getAbsolutePath());
+    }
+
+    private void checkSpace(long expected, long actual) {
+        if (expected == 0) {
+            assertEquals(0L, actual);
+        } else {
+            assertTrue(actual > 0);
         }
     }
+
+    @Test
+    public void getFreeSpace() throws IOException {
+        FileStore fs = Files.getFileStore(f.toPath());
+        checkSpace(fs.getUnallocatedSpace(), f.getFreeSpace());
+    }
+
+    @Test
+    public void getName() {
+        assertEquals(p.getFileName().toString(), f.getName());
+    }
+
+    @Test
+    public void getParent() {
+        assertNull(f.getParent());
+    }
+
+    @Test
+    public void getPath() {
+        assertEquals(p.toString(), f.getPath());
+    }
+
+    @Test
+    public void getTotalSpace() throws IOException {
+        FileStore fs = Files.getFileStore(f.toPath());
+        checkSpace(fs.getTotalSpace(), f.getTotalSpace());
+    }
+
+    @Test
+    public void getUsableSpace() throws IOException {
+        FileStore fs = Files.getFileStore(f.toPath());
+        checkSpace(fs.getUsableSpace(), f.getUsableSpace());
+    }
+
+    @Test
+    public void isNotAbsolute() {
+        assertFalse(f.isAbsolute());
+    }
+
+    @Test
+    public void isAbsolute() {
+        assertTrue(f.getAbsoluteFile().isAbsolute());
+    }
+
+    @Test
+    public void isDirectory() {
+        assertTrue(f.isDirectory());
+    }
+
+    @Test
+    public void isFile() {
+        assertFalse(f.isFile());
+    }
+
+    @Test
+    public void isHidden() {
+        assertFalse(f.isHidden());
+    }
+
+    @Test
+    public void lastModified() {
+        assertTrue(f.lastModified() > 0);
+    }
+
+    @Test
+    public void length() throws IOException {
+        assertEquals(Files.size(f.toPath()), f.length());
+    }
+
+    @Test
+    public void list() throws IOException {
+        String[] files = f.list();
+        assertNotNull(files);
+        Set<String> ioSet = new HashSet(Arrays.asList(files));
+        Set<String> nioSet = new HashSet();
+        Files.list(p).forEach((x) -> nioSet.add(x.toString()));
+        assertEquals(nioSet, ioSet);
+    }
+
+    @Test
+    public void mkdir() {
+        assertFalse(f.mkdir());
+    }
+
+    @Test
+    public void setLastModified() {
+        long t0 = f.lastModified();
+        long t = System.currentTimeMillis();
+        try {
+            assertTrue(f.setLastModified(t));
+            assertEquals(t, f.lastModified());
+            assertTrue(f.setLastModified(t0));
+            assertEquals(t0, f.lastModified());
+        } finally {
+            f.setLastModified(t0);
+        }
+    }
+
+    // Note: Testing File.setExecutable is omitted because calling
+    // File.setExecutable(false) makes it impossible to set the CWD to
+    // executable again which makes subsequent tests fail
+
+    @Test
+    @DisabledOnOs({OS.WINDOWS})
+    public void setReadable() {
+        assertTrue(f.canRead());
+        try {
+            assertTrue(f.setReadable(false));
+            assertFalse(f.canRead());
+            assertTrue(f.setReadable(true));
+            assertTrue(f.canRead());
+        } finally {
+            f.setReadable(true);
+        }
+    }
+
+    @Test
+    @DisabledOnOs({OS.WINDOWS})
+    public void setReadOnly() {
+        assertTrue(f.canExecute());
+        assertTrue(f.canRead());
+        assertTrue(f.canWrite());
+        try {
+            assertTrue(f.setReadOnly());
+            assertTrue(f.canRead());
+            assertFalse(f.canWrite());
+            assertTrue(f.setWritable(true, true));
+            assertTrue(f.canWrite());
+        } finally {
+            f.setWritable(true, true);
+        }
+    }
+
+    @Test
+    @DisabledOnOs({OS.WINDOWS})
+    public void setWritable() {
+        assertTrue(f.canWrite());
+        try {
+            assertTrue(f.setWritable(false, true));
+            assertFalse(f.canWrite());
+            assertTrue(f.setWritable(true, true));
+            assertTrue(f.canWrite());
+        } finally {
+            f.setWritable(true, true);
+        }
+    }
+
+    @Test
+    public void toPath() {
+        assertEquals(p, f.toPath());
+    }
+
+    @Test
+    public void toURI() {
+        assertEquals(f.toPath().toUri(), f.toURI());
+    }
 }