src/org/nutz/lang/Files.java
public static String getSuffix(String path) {
        if (null == path)
            return null;
        int p0 = path.lastIndexOf('.');
        int p1 = path.lastIndexOf('/');
        if (-1 == p0 || p0 < p1)
            return "";
        return path.substring(p0);
    }
public static String getSuffix(String path) {
        if (null == path)
            return null;
        int p0 = path.lastIndexOf('.');
        int p1 = path.lastIndexOf('/');
        if (-1 == p0 || p0 < p1)
            return "";
        return path.substring(p0);
    }
获取文件后缀名，包括 '.'，如 'abc.gif','，则返回 '.gif'

@param path
文件路径
@return 文件后缀