change extName

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

@@ -222,6 +222,11 @@ public class FileNameUtil {
 		if (index == -1) {
 			return StrUtil.EMPTY;
 		} else {
+			// issue#I4W5FS@Gitee
+			if(fileName.endsWith("tar.gz")){
+				return "tar.gz";
+			}
+
 			String ext = fileName.substring(index + 1);
 			// 扩展名中不能包含路径相关的符号
 			return StrUtil.containsAny(ext, UNIX_SEPARATOR, WINDOWS_SEPARATOR) ? StrUtil.EMPTY : ext;

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

@@ -392,6 +392,10 @@ public class FileUtilTest {
 		path = FileUtil.isWindows() ? "d:\\aaa\\bbb\\cc\\fff.xlsx" : "~/Desktop/hutool/fff.xlsx";
 		mainName = FileUtil.extName(path);
 		Assert.assertEquals("xlsx", mainName);
+
+		path = FileUtil.isWindows() ? "d:\\aaa\\bbb\\cc\\fff.tar.gz" : "~/Desktop/hutool/fff.tar.gz";
+		mainName = FileUtil.extName(path);
+		Assert.assertEquals("tar.gz", mainName);
 	}
 
 	@Test