针对issue#I4W5FS@Gitee存在其他特殊情况处理

hutool-core/src/main/java/cn/hutool/core/io/file/FileNameUtil.java

@@ -42,6 +42,11 @@ public class FileNameUtil {
 	 */
 	private static final Pattern FILE_NAME_INVALID_PATTERN_WIN = Pattern.compile("[\\\\/:*?\"<>|]");
 
+	/**
+	 * 特殊后缀
+	 */
+	private static final CharSequence[] SPECIAL_SUFFIX = {"tar.bz2", "tar.Z", "tar.gz"};
+
 
 	// -------------------------------------------------------------------------------------------- name start
 
@@ -223,8 +228,10 @@ public class FileNameUtil {
 			return StrUtil.EMPTY;
 		} else {
 			// issue#I4W5FS@Gitee
-			if(fileName.endsWith("tar.gz")){
+			int secondToLastIndex = fileName.substring(0, index).lastIndexOf(StrUtil.DOT);
-				return "tar.gz";
+			String substr = fileName.substring(secondToLastIndex == -1 ? index : secondToLastIndex + 1);
+			if (StrUtil.containsAny(substr, SPECIAL_SUFFIX)) {
+				return substr;
 			}
 
 			String ext = fileName.substring(index + 1);

hutool-core/src/test/java/cn/hutool/core/io/FileUtilTest.java

@@ -396,6 +396,14 @@ public class FileUtilTest {
 		path = FileUtil.isWindows() ? "d:\\aaa\\bbb\\cc\\fff.tar.gz" : "~/Desktop/hutool/fff.tar.gz";
 		mainName = FileUtil.extName(path);
 		Assert.assertEquals("tar.gz", mainName);
+
+		path = FileUtil.isWindows() ? "d:\\aaa\\bbb\\cc\\fff.tar.Z" : "~/Desktop/hutool/fff.tar.Z";
+		mainName = FileUtil.extName(path);
+		Assert.assertEquals("tar.Z", mainName);
+
+		path = FileUtil.isWindows() ? "d:\\aaa\\bbb\\cc\\fff.tar.bz2" : "~/Desktop/hutool/fff.tar.bz2";
+		mainName = FileUtil.extName(path);
+		Assert.assertEquals("tar.bz2", mainName);
 	}
 
 	@Test