diff --git a/common/src/main/java/com/micro/fast/common/util/FileUtil.java b/common/src/main/java/com/micro/fast/common/util/FileUtil.java
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+++ b/common/src/main/java/com/micro/fast/common/util/FileUtil.java
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+package com.micro.fast.common.util;
+
+import java.io.File;
+/**
+ * 文件操作工具类
+ * create by lishouyu 2017/08/27
+ * email 18332763730@163.com
+ *
+ * last edit lishouyu 2017/08/27
+ * email 18332763730@163.com
+ * 添加递归修改文件夹下所有特定文件的扩展名的方法
+ */
+public class FileUtil {
+    /**
+     * 修改文件夹下的所有符合条件的文件的扩展名，递归文件夹下所有文件
+     * @param dir 文件夹下的路径
+     * @param oldExtensionName 旧的文件扩展名
+     * @param newExtensionName 新的文件扩展名
+     */
+    public static void ModifyFileExtensionNameInDir(File dir,String oldExtensionName,String newExtensionName){
+        //判断输入的文件是否是文件夹
+        boolean isdirectory = dir.isDirectory();
+        if (isdirectory==true){
+            //获取目录下的所有的文件以及目录
+            File[] files = dir.listFiles();
+            if (files.length>0){
+                for (File file:files){
+                    if (file.isDirectory()){
+                        ModifyFileExtensionNameInDir(file,oldExtensionName,newExtensionName);
+                    }else{
+                        String fileName = file.getName();
+                        if (fileName.endsWith(oldExtensionName)){
+                            //去掉扩展名
+                            int lastIndexOfPoint = fileName.lastIndexOf('.');
+                            String newFilename = fileName.substring(0, lastIndexOfPoint);
+                            //重命名文件
+                            file.renameTo(new File(file.getParent()+"/"+newFilename+newExtensionName));
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/common/src/main/java/com/micro/fast/common/util/My.java b/common/src/main/java/com/micro/fast/common/util/My.java
new file mode 100644
index 0000000..bd03401
--- /dev/null
+++ b/common/src/main/java/com/micro/fast/common/util/My.java
@@ -0,0 +1,16 @@
+package com.micro.fast.common.util;
+
+
+public class My {
+    private static final String world="李新";
+    @Override
+    public final String toString() {
+        return My.world;
+    }
+
+    public static void main(String[] args) {
+        My my= new My();
+        System.out.println(my.world);
+    }
+}
+
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