diff --git a/src/main/java/org/apache/commons/io/FileUtils.java b/src/main/java/org/apache/commons/io/FileUtils.java
index 363ab69f4b0..0c315204fec 100644
--- a/src/main/java/org/apache/commons/io/FileUtils.java
+++ b/src/main/java/org/apache/commons/io/FileUtils.java
@@ -293,6 +293,7 @@ public static String byteCountToDisplaySize(final Number size) {
      * @throws NullPointerException if the given {@link File} is {@code null}.
      * @throws NullPointerException if the given {@link Checksum} is {@code null}.
      * @throws IllegalArgumentException if the given {@link File} is not a file.
+     * @throws FileNotFoundException if the file does not exist
      * @throws IOException if an IO error occurs reading the file.
      * @since 1.3
      */
@@ -377,8 +378,12 @@ public static boolean contentEquals(final File file1, final File file2) throws I
             return true;
         }
 
-        checkFileExists(file1, "file1");
-        checkFileExists(file2, "file2");
+        if (!file1.isFile()) {
+            throw new IllegalArgumentException("Parameter 'file1' is not a file: " + file1);
+        }
+        if (!file2.isFile()) {
+            throw new IllegalArgumentException("Parameter 'file2' is not a file: " + file2);
+        }
 
         if (file1.length() != file2.length()) {
             // lengths differ, cannot be equal
@@ -663,7 +668,7 @@ public static void copyDirectory(final File srcDir, final File destDir, final Fi
      */
     public static void copyDirectory(final File srcDir, final File destDir, final FileFilter fileFilter, final boolean preserveFileDate,
         final CopyOption... copyOptions) throws IOException {
-        requireFileCopy(srcDir, destDir);
+        Objects.requireNonNull(destDir, "destination");
         requireDirectoryExists(srcDir, "srcDir");
         requireCanonicalPathsNotEquals(srcDir, destDir);
 
@@ -709,7 +714,7 @@ public static void copyDirectory(final File srcDir, final File destDir, final Fi
      * @since 1.2
      */
     public static void copyDirectoryToDirectory(final File sourceDir, final File destinationDir) throws IOException {
-        requireDirectoryIfExists(sourceDir, "sourceDir");
+        Objects.requireNonNull(sourceDir, "sourceDir");
         requireDirectoryIfExists(destinationDir, "destinationDir");
         copyDirectory(sourceDir, new File(destinationDir, sourceDir.getName()), true);
     }
@@ -795,11 +800,10 @@ public static void copyFile(final File srcFile, final File destFile, final boole
      * @since 2.8.0
      */
     public static void copyFile(final File srcFile, final File destFile, final boolean preserveFileDate, final CopyOption... copyOptions) throws IOException {
-        requireFileCopy(srcFile, destFile);
+        Objects.requireNonNull(destFile, "destination");
         checkFileExists(srcFile, "srcFile");
         requireCanonicalPathsNotEquals(srcFile, destFile);
         createParentDirectories(destFile);
-        Objects.requireNonNull(destFile, "destFile");
         if (destFile.exists()) {
             checkFileExists(destFile, "destFile");
             requireCanWrite(destFile, "destFile");
@@ -1249,7 +1253,7 @@ public static boolean deleteQuietly(final File file) {
      *
      * Edge cases:
      * <ul>
-     * <li>A {@code directory} must not be null: if null, throw IllegalArgumentException</li>
+     * <li>A {@code directory} must not be null: if null, throw NullPointerException</li>
      * <li>A {@code directory} must be a directory: if not a directory, throw IllegalArgumentException</li>
      * <li>A directory does not contain itself: return false</li>
      * <li>A null child file is not contained in any parent: return false</li>
@@ -1267,7 +1271,7 @@ public static boolean deleteQuietly(final File file) {
     public static boolean directoryContains(final File directory, final File child) throws IOException {
         requireDirectoryExists(directory, "directory");
 
-        if (child == null || !directory.exists() || !child.exists()) {
+        if (child == null || !child.exists()) {
             return false;
         }
 
@@ -1328,14 +1332,15 @@ private static void doCopyDirectory(final File srcDir, final File destDir, final
      */
     public static void forceDelete(final File file) throws IOException {
         Objects.requireNonNull(file, "file");
+
         final Counters.PathCounters deleteCounters;
         try {
-            deleteCounters = PathUtils.delete(file.toPath(), PathUtils.EMPTY_LINK_OPTION_ARRAY,
-                StandardDeleteOption.OVERRIDE_READ_ONLY);
-        } catch (final IOException e) {
-            throw new IOException("Cannot delete file: " + file, e);
+            deleteCounters = PathUtils.delete(
+                    file.toPath(), PathUtils.EMPTY_LINK_OPTION_ARRAY,
+                    StandardDeleteOption.OVERRIDE_READ_ONLY);
+        } catch (final IOException ex) {
+            throw new IOException("Cannot delete file: " + file, ex);
         }
-
         if (deleteCounters.getFileCounter().get() < 1 && deleteCounters.getDirectoryCounter().get() < 1) {
             // didn't find a file to delete.
             throw new FileNotFoundException("File does not exist: " + file);
@@ -1533,6 +1538,7 @@ public static boolean isEmptyDirectory(final File directory) throws IOException
      * @param chronoLocalDate the date reference.
      * @return true if the {@link File} exists and has been modified after the given
      * {@link ChronoLocalDate} at the current time.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file or local date is {@code null}.
      * @since 2.8.0
      */
@@ -1554,6 +1560,7 @@ public static boolean isFileNewer(final File file, final ChronoLocalDate chronoL
      * @param localTime       the time reference.
      * @return true if the {@link File} exists and has been modified after the given
      * {@link ChronoLocalDate} at the given time.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file, local date or zone ID is {@code null}.
      * @since 2.8.0
      */
@@ -1572,6 +1579,7 @@ public static boolean isFileNewer(final File file, final ChronoLocalDate chronoL
      * @param offsetTime the time reference
      * @return true if the {@link File} exists and has been modified after the given {@link ChronoLocalDate} at the given
      *         {@link OffsetTime}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file, local date or zone ID is {@code null}
      * @since 2.12.0
      */
@@ -1594,6 +1602,7 @@ public static boolean isFileNewer(final File file, final ChronoLocalDate chronoL
      * @param chronoLocalDateTime the date reference.
      * @return true if the {@link File} exists and has been modified after the given
      * {@link ChronoLocalDateTime} at the system-default time zone.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file or local date time is {@code null}.
      * @since 2.8.0
      */
@@ -1610,6 +1619,7 @@ public static boolean isFileNewer(final File file, final ChronoLocalDateTime<?>
      * @param zoneId              the time zone.
      * @return true if the {@link File} exists and has been modified after the given
      * {@link ChronoLocalDateTime} at the given {@link ZoneId}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file, local date time or zone ID is {@code null}.
      * @since 2.8.0
      */
@@ -1627,6 +1637,7 @@ public static boolean isFileNewer(final File file, final ChronoLocalDateTime<?>
      * @return true if the {@link File} exists and has been modified after the given
      * {@link ChronoZonedDateTime}.
      * @throws NullPointerException if the file or zoned date time is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @since 2.8.0
      */
     public static boolean isFileNewer(final File file, final ChronoZonedDateTime<?> chronoZonedDateTime) {
@@ -1642,6 +1653,7 @@ public static boolean isFileNewer(final File file, final ChronoZonedDateTime<?>
      * @param date the date reference.
      * @return true if the {@link File} exists and has been modified
      * after the given {@link Date}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file or date is {@code null}.
      */
     public static boolean isFileNewer(final File file, final Date date) {
@@ -1685,6 +1697,7 @@ public static boolean isFileNewer(final File file, final FileTime fileTime) thro
      * @param instant the date reference.
      * @return true if the {@link File} exists and has been modified after the given {@link Instant}.
      * @throws NullPointerException if the file or instant is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @since 2.8.0
      */
     public static boolean isFileNewer(final File file, final Instant instant) {
@@ -1699,6 +1712,7 @@ public static boolean isFileNewer(final File file, final Instant instant) {
      * @param timeMillis the time reference measured in milliseconds since the
      *                   epoch (00:00:00 GMT, January 1, 1970).
      * @return true if the {@link File} exists and has been modified after the given time reference.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file is {@code null}.
      */
     public static boolean isFileNewer(final File file, final long timeMillis) {
@@ -1712,6 +1726,7 @@ public static boolean isFileNewer(final File file, final long timeMillis) {
      * @param file the {@link File} of which the modification date must be compared
      * @param offsetDateTime the date reference
      * @return true if the {@link File} exists and has been modified before the given {@link OffsetDateTime}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file or zoned date time is {@code null}
      * @since 2.12.0
      */
@@ -1735,6 +1750,7 @@ public static boolean isFileNewer(final File file, final OffsetDateTime offsetDa
      * @return true if the {@link File} exists and has been modified before the given
      * {@link ChronoLocalDate} at the current time.
      * @throws NullPointerException if the file or local date is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @see ZoneId#systemDefault()
      * @see LocalTime#now()
      * @since 2.8.0
@@ -1757,6 +1773,7 @@ public static boolean isFileOlder(final File file, final ChronoLocalDate chronoL
      * @param localTime       the time reference.
      * @return true if the {@link File} exists and has been modified before the
      * given {@link ChronoLocalDate} at the specified time.
+     * @throws UncheckedIOException if an I/O error occurs
      * @throws NullPointerException if the file, local date or local time is {@code null}.
      * @see ZoneId#systemDefault()
      * @since 2.8.0
@@ -1777,6 +1794,7 @@ public static boolean isFileOlder(final File file, final ChronoLocalDate chronoL
      * @return true if the {@link File} exists and has been modified after the given {@link ChronoLocalDate} at the given
      *         {@link OffsetTime}.
      * @throws NullPointerException if the file, local date or zone ID is {@code null}
+     * @throws UncheckedIOException if an I/O error occurs
      * @since 2.12.0
      */
     public static boolean isFileOlder(final File file, final ChronoLocalDate chronoLocalDate, final OffsetTime offsetTime) {
@@ -1799,6 +1817,7 @@ public static boolean isFileOlder(final File file, final ChronoLocalDate chronoL
      * @return true if the {@link File} exists and has been modified before the given
      * {@link ChronoLocalDateTime} at the system-default time zone.
      * @throws NullPointerException if the file or local date time is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @see ZoneId#systemDefault()
      * @since 2.8.0
      */
@@ -1816,6 +1835,7 @@ public static boolean isFileOlder(final File file, final ChronoLocalDateTime<?>
      * @return true if the {@link File} exists and has been modified before the given
      * {@link ChronoLocalDateTime} at the given {@link ZoneId}.
      * @throws NullPointerException if the file, local date time or zone ID is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @since 2.8.0
      */
     public static boolean isFileOlder(final File file, final ChronoLocalDateTime<?> chronoLocalDateTime, final ZoneId zoneId) {
@@ -1832,6 +1852,7 @@ public static boolean isFileOlder(final File file, final ChronoLocalDateTime<?>
      * @return true if the {@link File} exists and has been modified before the given
      * {@link ChronoZonedDateTime}.
      * @throws NullPointerException if the file or zoned date time is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      * @since 2.8.0
      */
     public static boolean isFileOlder(final File file, final ChronoZonedDateTime<?> chronoZonedDateTime) {
@@ -1846,6 +1867,7 @@ public static boolean isFileOlder(final File file, final ChronoZonedDateTime<?>
      * @param date the date reference.
      * @return true if the {@link File} exists and has been modified before the given {@link Date}.
      * @throws NullPointerException if the file or date is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      */
     public static boolean isFileOlder(final File file, final Date date) {
         Objects.requireNonNull(date, "date");
@@ -1859,7 +1881,8 @@ public static boolean isFileOlder(final File file, final Date date) {
      * @param reference the {@link File} of which the modification date is used.
      * @return true if the {@link File} exists and has been modified before the reference {@link File}.
      * @throws NullPointerException if the file or reference file is {@code null}.
-     * @throws IllegalArgumentException if the reference file doesn't exist.
+     * @throws FileNotFoundException if the reference file doesn't exist.
+     * @throws UncheckedIOException if an I/O error occurs
      */
     public static boolean isFileOlder(final File file, final File reference) throws FileNotFoundException {
         return Uncheck.get(() -> PathUtils.isOlder(file.toPath(), reference.toPath()));
@@ -1902,6 +1925,7 @@ public static boolean isFileOlder(final File file, final Instant instant) {
      *                   epoch (00:00:00 GMT, January 1, 1970).
      * @return true if the {@link File} exists and has been modified before the given time reference.
      * @throws NullPointerException if the file is {@code null}.
+     * @throws UncheckedIOException if an I/O error occurs
      */
     public static boolean isFileOlder(final File file, final long timeMillis) {
         Objects.requireNonNull(file, "file");
@@ -2304,7 +2328,7 @@ private static File mkdirs(final File directory) throws IOException {
      * @since 1.4
      */
     public static void moveDirectory(final File srcDir, final File destDir) throws IOException {
-        validateMoveParameters(srcDir, destDir);
+        Objects.requireNonNull(destDir, "destination");
         requireDirectoryExists(srcDir, "srcDir");
         requireAbsent(destDir, "destDir");
         if (!srcDir.renameTo(destDir)) {
@@ -2326,7 +2350,7 @@ public static void moveDirectory(final File srcDir, final File destDir) throws I
      * If {@code createDestDir} is true, creates all destination parent directories, including any necessary but non-existent parent directories.
      * </p>
      *
-     * @param source the file to be moved.
+     * @param source the directory to be moved.
      * @param destDir the destination file.
      * @param createDestDir If {@code true} create the destination directory, otherwise if {@code false} throw an
      *        IOException.
@@ -2391,7 +2415,7 @@ public static void moveFile(final File srcFile, final File destFile) throws IOEx
      * @since 2.9.0
      */
     public static void moveFile(final File srcFile, final File destFile, final CopyOption... copyOptions) throws IOException {
-        validateMoveParameters(srcFile, destFile);
+        Objects.requireNonNull(destFile, "destination");
         checkFileExists(srcFile, "srcFile");
         requireAbsent(destFile, "destFile");
         final boolean rename = srcFile.renameTo(destFile);
@@ -2406,15 +2430,15 @@ public static void moveFile(final File srcFile, final File destFile, final CopyO
     }
 
     /**
-     * Moves a file to a directory.
+     * Moves a file into a directory.
      * <p>
      * If {@code createDestDir} is true, creates all destination parent directories, including any necessary but non-existent parent directories.
      * </p>
      *
      * @param srcFile the file to be moved.
-     * @param destDir the destination file.
-     * @param createDestDir If {@code true} create the destination directory, otherwise if {@code false} throw an
-     *        IOException.
+     * @param destDir the directory to move the file into
+     * @param createDestDir if {@code true} create the destination directory. If {@code false} throw an
+     *        IOException if the destination directory does not already exist.
      * @throws NullPointerException if any of the given {@link File}s are {@code null}.
      * @throws FileExistsException if the destination file exists.
      * @throws FileNotFoundException if the source file does not exist.
@@ -2434,7 +2458,7 @@ public static void moveFileToDirectory(final File srcFile, final File destDir, f
     }
 
     /**
-     * Moves a file or directory to a destination directory.
+     * Moves a file or directory into a destination directory.
      * <p>
      * If {@code createDestDir} is true, creates all destination parent directories, including any necessary but non-existent parent directories.
      * </p>
@@ -2444,7 +2468,8 @@ public static void moveFileToDirectory(final File srcFile, final File destDir, f
      *
      * @param src           the file or directory to be moved.
      * @param destDir       the destination directory.
-     * @param createDestDir If {@code true} create the destination directory, otherwise if {@code false} throw an IOException.
+     * @param createDestDir if {@code true} create the destination directory. If {@code false} throw an
+     *        IOException if the destination directory does not already exist.
      * @throws NullPointerException  if any of the given {@link File}s are {@code null}.
      * @throws FileExistsException   if the directory or file exists in the destination directory.
      * @throws FileNotFoundException if the source file does not exist.
@@ -2555,7 +2580,9 @@ public static FileOutputStream openOutputStream(final File file) throws IOExcept
     public static FileOutputStream openOutputStream(final File file, final boolean append) throws IOException {
         Objects.requireNonNull(file, "file");
         if (file.exists()) {
-            checkFileExists(file, "file");
+            if (!file.isFile()) {
+                throw new IllegalArgumentException("Parameter 'file' is not a file: " + file);
+            }
             requireCanWrite(file, "file");
         } else {
             createParentDirectories(file);
@@ -2711,7 +2738,6 @@ private static void requireCanonicalPathsNotEquals(final File file1, final File
      * @throws IllegalArgumentException if the file is not writable.
      */
     private static void requireCanWrite(final File file, final String name) {
-        Objects.requireNonNull(file, "file");
         if (!file.canWrite()) {
             throw new IllegalArgumentException("File parameter '" + name + " is not writable: '" + file + "'");
         }
@@ -2741,50 +2767,29 @@ private static void requireDirectoryExists(final File directory, final String na
      *
      * @param directory The {@link File} to check.
      * @param name The parameter name to use in the exception message in case of null input.
-     * @throws FileNotFoundException if the given {@link File} does not exist
      * @throws NullPointerException if the given {@link File} is {@code null}.
      * @throws IllegalArgumentException if the given {@link File} exists but is not a directory.
      */
     private static void requireDirectoryIfExists(final File directory, final String name) throws FileNotFoundException {
         Objects.requireNonNull(directory, name);
-        if (directory.exists()) {
-            requireDirectoryExists(directory, name);
-        }
-    }
-
-    /**
-     * Requires that the given {@link File} object, which may be a file or a directory,
-     * points to an actually existing item in the file system,
-     * and throws a {@link FileNotFoundException} if it doesn't.
-     *
-     * @param file The {@link File} to check.
-     * @param fileParamName The parameter name to use in the exception message in case of {@code null} input.
-     * @return the given file.
-     * @throws NullPointerException if the given {@link File} is {@code null}.
-     * @throws FileNotFoundException if the given {@link File} does not exist.
-     */
-    private static File checkFileObjectExists(final File file, final String fileParamName) throws FileNotFoundException {
-        Objects.requireNonNull(file, fileParamName);
-        if (!file.exists()) {
-            throw new FileNotFoundException("File system element for parameter '" + fileParamName + "' does not exist: '" + file + "'");
+        if (directory.exists() && !directory.isDirectory()) {
+            throw new IllegalArgumentException("Parameter '" + name + "' is not a directory: '" + directory + "'");
         }
-        return file;
     }
 
     /**
-     * Requires that the given {@link File} object,
+     * Requires that the given {@link File} object
      * points to an actual file (not a directory) in the file system,
      * and throws a {@link FileNotFoundException} if it doesn't.
      * It throws an IllegalArgumentException if the object points to a directory.
      *
      * @param file The {@link File} to check.
      * @param name The parameter name to use in the exception message.
-     * @return the given file.
      * @throws FileNotFoundException if the file does not exist
      * @throws NullPointerException if the given {@link File} is {@code null}.
      * @throws IllegalArgumentException if the given {@link File} is not a file.
      */
-    private static File checkFileExists(final File file, final String name) throws FileNotFoundException {
+    private static void checkFileExists(final File file, final String name) throws FileNotFoundException {
         Objects.requireNonNull(file, name);
         if (!file.isFile()) {
             if (file.exists()) {
@@ -2792,20 +2797,6 @@ private static File checkFileExists(final File file, final String name) throws F
             }
             throw new FileNotFoundException("Source '" + file + "' does not exist");
         }
-        return file;
-    }
-
-    /**
-     * Requires parameter attributes for a file copy operation.
-     *
-     * @param source the source file
-     * @param destination the destination
-     * @throws NullPointerException if any of the given {@link File}s are {@code null}.
-     * @throws FileNotFoundException if the source does not exist.
-     */
-    private static void requireFileCopy(final File source, final File destination) throws FileNotFoundException {
-        checkFileObjectExists(source, "source");
-        Objects.requireNonNull(destination, "destination");
     }
 
     /**
@@ -3520,7 +3511,7 @@ public static void writeStringToFile(final File file, final String data, final S
 
     /**
      * Instances should NOT be constructed in standard programming.
-     * @deprecated Will be private in 3.0.
+     * @deprecated Will be private in 4.0.
      */
     @Deprecated
     public FileUtils() { //NOSONAR
diff --git a/src/main/java/org/apache/commons/io/function/IOConsumer.java b/src/main/java/org/apache/commons/io/function/IOConsumer.java
index e417178fc3e..e35ad7ef0e6 100644
--- a/src/main/java/org/apache/commons/io/function/IOConsumer.java
+++ b/src/main/java/org/apache/commons/io/function/IOConsumer.java
@@ -67,7 +67,7 @@ static <T> void forAll(final IOConsumer<T> action, final Stream<T> stream) throw
     }
 
     /**
-     * Performs an action for each element of the array gathering any exceptions.
+     * Performs an action for each element of the array, gathering any exceptions.
      *
      * @param action The action to apply to each input element.
      * @param array The input to stream.
diff --git a/src/test/java/org/apache/commons/io/FileUtilsCopyDirectoryToDirectoryTest.java b/src/test/java/org/apache/commons/io/FileUtilsCopyDirectoryToDirectoryTest.java
index e4032f86924..cce762bd3f1 100644
--- a/src/test/java/org/apache/commons/io/FileUtilsCopyDirectoryToDirectoryTest.java
+++ b/src/test/java/org/apache/commons/io/FileUtilsCopyDirectoryToDirectoryTest.java
@@ -77,7 +77,7 @@ public void testCopyDirectoryToDirectoryThrowsIllegalExceptionWithCorrectMessage
         try (TempFile srcDir = TempFile.create("notadirectory", null)) {
             final File destDir = new File(temporaryFolder, "destinationDirectory");
             destDir.mkdirs();
-            final String expectedMessage = String.format("Parameter 'sourceDir' is not a directory: '%s'", srcDir);
+            final String expectedMessage = String.format("Parameter 'srcDir' is not a directory: '%s'", srcDir);
             assertExceptionTypeAndMessage(srcDir.toFile(), destDir, IllegalArgumentException.class, expectedMessage);
         }
     }
diff --git a/src/test/java/org/apache/commons/io/FileUtilsDeleteDirectoryLinuxTest.java b/src/test/java/org/apache/commons/io/FileUtilsDeleteDirectoryLinuxTest.java
index 60600ff57d9..ad50f2f8170 100644
--- a/src/test/java/org/apache/commons/io/FileUtilsDeleteDirectoryLinuxTest.java
+++ b/src/test/java/org/apache/commons/io/FileUtilsDeleteDirectoryLinuxTest.java
@@ -88,7 +88,8 @@ public void testThrowsOnCannotDeleteFile() throws Exception {
         try {
             // deleteDirectory calls forceDelete
             final IOExceptionList ioExceptionList = (IOExceptionList) assertThrows(IOException.class, () -> FileUtils.deleteDirectory(nested));
-            assertTrue(ioExceptionList.getCause(0).getMessage().endsWith("Cannot delete file: " + file.getAbsolutePath()));
+            final String message = ioExceptionList.getCause(0).getMessage();
+            assertTrue(message.endsWith("Cannot delete file: " + file.getAbsolutePath()), message);
         } finally {
             chmod(nested, 755, false);
             FileUtils.deleteDirectory(nested);