Handling null charset in FileUtils.readLines(File, Charset) (#744)

Author: ryanmkurtz

src/main/java/org/apache/commons/io/FileUtils.java

@@ -2817,7 +2817,7 @@ public static List<String> readLines(final File file) throws IOException {
      * @since 2.3
      */
     public static List<String> readLines(final File file, final Charset charset) throws IOException {
-        return Files.readAllLines(file.toPath(), charset);
+        return Files.readAllLines(file.toPath(), Charsets.toCharset(charset));
     }
 
     /**

src/test/java/org/apache/commons/io/FileUtilsTest.java

@@ -2839,6 +2839,25 @@ public void testReadLines_Errors() {
         assertThrows(UnsupportedCharsetException.class, () -> FileUtils.readLines(tempDirFile, "unsupported-charset"));
     }
 
+    @Test
+    public void testReadLines_Defaults() throws Exception {
+        final File file = TestUtils.newFile(tempDirFile, "lines.txt");
+        try {
+            final String[] data = {"hello", "this is", "some text"};
+            TestUtils.createLineFileUtf8(file, data);
+
+            final List<String> lines1 = FileUtils.readLines(file);
+            final List<String> lines2 = FileUtils.readLines(file, (Charset) null);
+            final List<String> lines3 = FileUtils.readLines(file, Charset.defaultCharset());
+
+            assertEquals(lines1, Arrays.asList(data));
+            assertEquals(lines1, lines2);
+            assertEquals(lines1, lines3);
+        } finally {
+            TestUtils.deleteFile(file);
+        }
+    }
+
     @Test
     @EnabledIf("isPosixFilePermissionsSupported")
     public void testReadLines_IOExceptionOnPosixFileSystem() throws Exception {