diff --git a/src/main/java/com/qiniu/storage/BucketManager.java b/src/main/java/com/qiniu/storage/BucketManager.java
index b801e57c1..3c0bad223 100644
--- a/src/main/java/com/qiniu/storage/BucketManager.java
+++ b/src/main/java/com/qiniu/storage/BucketManager.java
@@ -11,6 +11,7 @@
 import com.qiniu.util.StringMap;
 import com.qiniu.util.StringUtils;
 import com.qiniu.util.UrlSafeBase64;
+
 import java.util.ArrayList;
 import java.util.Iterator;
 
@@ -20,421 +21,402 @@
  * @link http://developer.qiniu.com/docs/v6/api/reference/rs/
  */
 public final class BucketManager {
-	private final Auth auth;
-	private final Client client;
-
-	public BucketManager(Auth auth) {
-		this.auth = auth;
-		client = new Client();
-	}
-
-	/**
-	 * EncodedEntryURI格式
-	 *
-	 * @param bucket
-	 * @param key
-	 * @return urlsafe_base64_encode(Bucket:Key)
-	 */
-	public static String entry(String bucket, String key) {
-		return entry(bucket, key, true);
-	}
-
-	/**
-	 * EncodedEntryURI格式 当 mustHaveKey 为 false， 且 key 为 null 时，返回
-	 * urlsafe_base64_encode(Bucket); 其它条件下返回 urlsafe_base64_encode(Bucket:Key)
-	 *
-	 * @param bucket
-	 * @param key
-	 * @param mustHaveKey
-	 * @return urlsafe_base64_encode(entry)
-	 */
-	public static String entry(String bucket, String key, boolean mustHaveKey) {
-		String en = bucket + ":" + key;
-		if (!mustHaveKey && (key == null)) {
-			en = bucket;
-		}
-		return UrlSafeBase64.encodeToString(en);
-	}
-
-	/**
-	 * 获取账号下所有空间名列表
-	 *
-	 * @return bucket 列表
-	 */
-	public String[] buckets() throws QiniuException {
-		Response r = rsGet("/buckets");
-		return r.jsonToObject(String[].class);
-	}
-
-	/**
-	 * 根据前缀获取文件列表的迭代器
-	 *
-	 * @param bucket
-	 *            空间名
-	 * @param prefix
-	 *            文件名前缀
-	 * @return FileInfo迭代器
-	 */
-	public FileListIterator createFileListIterator(String bucket, String prefix) {
-		return new FileListIterator(bucket, prefix, 100, null);
-	}
-
-	/**
-	 * 根据前缀获取文件列表的迭代器
-	 *
-	 * @param bucket
-	 *            空间名
-	 * @param prefix
-	 *            文件名前缀
-	 * @param limit
-	 *            每次迭代的长度限制，最大1000，推荐值 100
-	 * @param delimiter
-	 *            指定目录分隔符，列出所有公共前缀（模拟列出目录效果）。缺省值为空字符串
-	 * @return FileInfo迭代器
-	 */
-	public FileListIterator createFileListIterator(String bucket, String prefix, int limit, String delimiter) {
-		return new FileListIterator(bucket, prefix, limit, delimiter);
-	}
-
-	/**
-	 * 根据前缀获取文件列表
-	 *
-	 * @param bucket
-	 *            空间名
-	 * @param prefix
-	 *            文件名前缀
-	 * @param marker
-	 *            上一次获取文件列表时返回的 marker
-	 * @param limit
-	 *            每次迭代的长度限制，最大1000，推荐值 100
-	 * @param delimiter
-	 *            指定目录分隔符，列出所有公共前缀（模拟列出目录效果）。缺省值为空字符串
-	 * @return
-	 * @throws QiniuException
-	 */
-	public FileListing listFiles(String bucket, String prefix, String marker, int limit, String delimiter)
-			throws QiniuException {
-		StringMap map = new StringMap().put("bucket", bucket).putNotEmpty("marker", marker)
-				.putNotEmpty("prefix", prefix).putNotEmpty("delimiter", delimiter).putWhen("limit", limit, limit > 0);
-
-		String url = Config.RSF_HOST + "/list?" + map.formString();
-		Response r = get(url);
-		return r.jsonToObject(FileListing.class);
-	}
-
-	/**
-	 * 获取指定空间、文件名的状态
-	 *
-	 * @param bucket
-	 * @param key
-	 * @return
-	 * @throws QiniuException
-	 */
-	public FileInfo stat(String bucket, String key) throws QiniuException {
-		Response r = rsGet("/stat/" + entry(bucket, key));
-		return r.jsonToObject(FileInfo.class);
-	}
-
-	/**
-	 * 删除指定空间、文件名的文件
-	 *
-	 * @param bucket
-	 * @param key
-	 * @throws QiniuException
-	 */
-	public void delete(String bucket, String key) throws QiniuException {
-		rsPost("/delete/" + entry(bucket, key));
-	}
-
-	/**
-	 * 修改指定空间、文件的文件名
-	 *
-	 * @param bucket
-	 * @param oldname
-	 * @param newname
-	 * @throws QiniuException
-	 */
-	public void rename(String bucket, String oldname, String newname) throws QiniuException {
-		move(bucket, oldname, bucket, newname);
-	}
-
-	/**
-	 * 复制文件。要求空间在同一账号下。
-	 *
-	 * @param from_bucket
-	 * @param from_key
-	 * @param to_bucket
-	 * @param to_key
-	 * @throws QiniuException
-	 */
-	public void copy(String from_bucket, String from_key, String to_bucket, String to_key) throws QiniuException {
-		String from = entry(from_bucket, from_key);
-		String to = entry(to_bucket, to_key);
-		String path = "/copy/" + from + "/" + to;
-		rsPost(path);
-	}
-
-	/**
-	 * 复制文件。要求空间在同一账号下, 可以添加force参数为true强行复制文件。
-	 *
-	 * @param from_bucket
-	 * @param from_key
-	 * @param to_bucket
-	 * @param to_key
-	 * @param force
-	 * @throws QiniuException
-	 */
-	public void copy(String from_bucket, String from_key, String to_bucket, String to_key, boolean force)
-			throws QiniuException {
-		String from = entry(from_bucket, from_key);
-		String to = entry(to_bucket, to_key);
-		String path = "/copy/" + from + "/" + to + "/force/" + force;
-		rsPost(path);
-	}
-
-	/**
-	 * 移动文件。要求空间在同一账号下。
-	 *
-	 * @param from_bucket
-	 * @param from_key
-	 * @param to_bucket
-	 * @param to_key
-	 * @throws QiniuException
-	 */
-	public void move(String from_bucket, String from_key, String to_bucket, String to_key) throws QiniuException {
-		String from = entry(from_bucket, from_key);
-		String to = entry(to_bucket, to_key);
-		String path = "/move/" + from + "/" + to;
-		rsPost(path);
-	}
-
-	/**
-	 * 移动文件。要求空间在同一账号下, 可以添加force参数为true强行移动文件。
-	 *
-	 * @param from_bucket
-	 * @param from_key
-	 * @param to_bucket
-	 * @param to_key
-	 * @param force
-	 * @throws QiniuException
-	 */
-	public void move(String from_bucket, String from_key, String to_bucket, String to_key, boolean force)
-			throws QiniuException {
-		String from = entry(from_bucket, from_key);
-		String to = entry(to_bucket, to_key);
-		String path = "/move/" + from + "/" + to + "/force/" + force;
-		rsPost(path);
-	}
-
-	/**
-	 * 修改完文件mimeTYpe
-	 *
-	 * @param bucket
-	 * @param key
-	 * @param mime
-	 * @throws QiniuException
-	 */
-	public void changeMime(String bucket, String key, String mime) throws QiniuException {
-		String resource = entry(bucket, key);
-		String encode_mime = UrlSafeBase64.encodeToString(mime);
-		String path = "/chgm/" + resource + "/mime/" + encode_mime;
-		rsPost(path);
-	}
-
-	/**
-	 * 抓取指定地址的文件，已指定名称保存在指定空间。 要求指定url可访问。 大文件不建议使用此接口抓取。可先下载再上传。
-	 *
-	 * @param url
-	 * @param bucket
-	 * @throws QiniuException
-	 */
-	public DefaultPutRet fetch(String url, String bucket) throws QiniuException {
-		return fetch(url, bucket, null);
-	}
-
-	/**
-	 * 抓取指定地址的文件，已指定名称保存在指定空间。 要求指定url可访问。 大文件不建议使用此接口抓取。可先下载再上传。
-	 *
-	 * @param url
-	 * @param bucket
-	 * @param key
-	 * @throws QiniuException
-	 */
-	public DefaultPutRet fetch(String url, String bucket, String key) throws QiniuException {
-		String resource = UrlSafeBase64.encodeToString(url);
-		String to = entry(bucket, key, false);
-		String path = "/fetch/" + resource + "/to/" + to;
-		Response r = ioPost(path);
-		return r.jsonToObject(DefaultPutRet.class);
-	}
-
-	/**
-	 * 对于设置了镜像存储的空间，从镜像源站抓取指定名称的资源并存储到该空间中。
-	 * 如果该空间中已存在该名称的资源，则会将镜像源站的资源覆盖空间中相同名称的资源
-	 *
-	 * @param bucket
-	 * @param key
-	 * @throws QiniuException
-	 */
-	public void prefetch(String bucket, String key) throws QiniuException {
-		String resource = entry(bucket, key);
-		String path = "/prefetch/" + resource;
-		ioPost(path);
-	}
-
-	/**
-	 * 批量执行文件管理相关操作
-	 *
-	 * @param operations
-	 * @return
-	 * @throws QiniuException
-	 * @see Batch
-	 */
-	public Response batch(Batch operations) throws QiniuException {
-		return rsPost("/batch", operations.toBody());
-	}
-
-	private Response rsPost(String path, byte[] body) throws QiniuException {
-		String url = Config.RS_HOST + path;
-		return post(url, body);
-	}
-
-	private Response rsPost(String path) throws QiniuException {
-		return rsPost(path, null);
-	}
-
-	private Response rsGet(String path) throws QiniuException {
-		String url = Config.RS_HOST + path;
-		return get(url);
-	}
-
-	private Response ioPost(String path) throws QiniuException {
-		String url = Config.IO_HOST + path;
-		return post(url, null);
-	}
-
-	private Response get(String url) throws QiniuException {
-		StringMap headers = auth.authorization(url);
-		return client.get(url, headers);
-	}
-
-	private Response post(String url, byte[] body) throws QiniuException {
-		StringMap headers = auth.authorization(url, body, Client.FormMime);
-		return client.post(url, body, headers, Client.FormMime);
-	}
-
-	/**
-	 * 文件管理操作指令
-	 */
-	public static class Batch {
-		private ArrayList<String> ops;
-
-		public Batch() {
-			this.ops = new ArrayList<String>();
-		}
-
-		public Batch copy(String from_bucket, String from_key, String to_bucket, String to_key) {
-			String from = entry(from_bucket, from_key);
-			String to = entry(to_bucket, to_key);
-			ops.add("copy" + "/" + from + "/" + to);
-			return this;
-		}
-
-		public Batch copy(String from_bucket, String from_key, String to_bucket, String to_key, boolean force) {
-			String from = entry(from_bucket, from_key);
-			String to = entry(to_bucket, to_key);
-			ops.add("copy" + "/" + from + "/" + to + "/force/" + force);
-			return this;
-		}
-
-		public Batch rename(String from_bucket, String from_key, String to_key) {
-			return move(from_bucket, from_key, from_bucket, to_key);
-		}
-
-		public Batch move(String from_bucket, String from_key, String to_bucket, String to_key) {
-			String from = entry(from_bucket, from_key);
-			String to = entry(to_bucket, to_key);
-			ops.add("move" + "/" + from + "/" + to);
-			return this;
-		}
-
-		public Batch move(String from_bucket, String from_key, String to_bucket, String to_key, boolean force) {
-			String from = entry(from_bucket, from_key);
-			String to = entry(to_bucket, to_key);
-			ops.add("move" + "/" + from + "/" + to + "/force/" + force);
-			return this;
-		}
-
-		public Batch delete(String bucket, String... keys) {
-			for (String key : keys) {
-				ops.add("delete" + "/" + entry(bucket, key));
-			}
-			return this;
-		}
-
-		public Batch stat(String bucket, String... keys) {
-			for (String key : keys) {
-				ops.add("stat" + "/" + entry(bucket, key));
-			}
-			return this;
-		}
-
-		public byte[] toBody() {
-			String body = StringUtils.join(ops, "&op=", "op=");
-			return StringUtils.utf8Bytes(body);
-		}
-
-		public Batch merge(Batch batch) {
-			this.ops.addAll(batch.ops);
-			return this;
-		}
-	}
-
-	/**
-	 * 获取文件列表迭代器
-	 */
-	public class FileListIterator implements Iterator<FileInfo[]> {
-		private String marker = null;
-		private String bucket;
-		private String delimiter;
-		private int limit;
-		private String prefix;
-		private QiniuException exception = null;
-
-		public FileListIterator(String bucket, String prefix, int limit, String delimiter) {
-			if (limit <= 0) {
-				throw new IllegalArgumentException("limit must great than 0");
-			}
-			this.bucket = bucket;
-			this.prefix = prefix;
-			this.limit = limit;
-			this.delimiter = delimiter;
-		}
-
-		public QiniuException error() {
-			return exception;
-		}
-
-		@Override
-		public boolean hasNext() {
-			return exception == null && !"".equals(marker);
-		}
-
-		@Override
-		public FileInfo[] next() {
-			try {
-				FileListing f = listFiles(bucket, prefix, marker, limit, delimiter);
-				this.marker = f.marker == null ? "" : f.marker;
-				return f.items;
-			} catch (QiniuException e) {
-				this.exception = e;
-				return null;
-			}
-		}
-
-		@Override
-		public void remove() {
-			throw new UnsupportedOperationException("remove");
-		}
-	}
+    private final Auth auth;
+    private final Client client;
+
+    public BucketManager(Auth auth) {
+        this.auth = auth;
+        client = new Client();
+    }
+
+    /**
+     * EncodedEntryURI格式
+     *
+     * @param bucket
+     * @param key
+     * @return urlsafe_base64_encode(Bucket:Key)
+     */
+    public static String entry(String bucket, String key) {
+        return entry(bucket, key, true);
+    }
+
+
+    /**
+     * EncodedEntryURI格式
+     * 当 mustHaveKey 为 false， 且 key 为 null 时，返回 urlsafe_base64_encode(Bucket);
+     * 其它条件下返回  urlsafe_base64_encode(Bucket:Key)
+     *
+     * @param bucket
+     * @param key
+     * @param mustHaveKey
+     * @return urlsafe_base64_encode(entry)
+     */
+    public static String entry(String bucket, String key, boolean mustHaveKey) {
+        String en = bucket + ":" + key;
+        if (!mustHaveKey && (key == null)) {
+            en = bucket;
+        }
+        return UrlSafeBase64.encodeToString(en);
+    }
+
+    /**
+     * 获取账号下所有空间名列表
+     *
+     * @return bucket 列表
+     */
+    public String[] buckets() throws QiniuException {
+        Response r = rsGet("/buckets");
+        return r.jsonToObject(String[].class);
+    }
+
+    /**
+     * 根据前缀获取文件列表的迭代器
+     *
+     * @param bucket 空间名
+     * @param prefix 文件名前缀
+     * @return FileInfo迭代器
+     */
+    public FileListIterator createFileListIterator(String bucket, String prefix) {
+        return new FileListIterator(bucket, prefix, 100, null);
+    }
+
+    /**
+     * 根据前缀获取文件列表的迭代器
+     *
+     * @param bucket    空间名
+     * @param prefix    文件名前缀
+     * @param limit     每次迭代的长度限制，最大1000，推荐值 100
+     * @param delimiter 指定目录分隔符，列出所有公共前缀（模拟列出目录效果）。缺省值为空字符串
+     * @return FileInfo迭代器
+     */
+    public FileListIterator createFileListIterator(String bucket, String prefix, int limit, String delimiter) {
+        return new FileListIterator(bucket, prefix, limit, delimiter);
+    }
+
+    /**
+     * 根据前缀获取文件列表
+     *
+     * @param bucket    空间名
+     * @param prefix    文件名前缀
+     * @param marker    上一次获取文件列表时返回的 marker
+     * @param limit     每次迭代的长度限制，最大1000，推荐值 100
+     * @param delimiter 指定目录分隔符，列出所有公共前缀（模拟列出目录效果）。缺省值为空字符串
+     * @return
+     * @throws QiniuException
+     */
+    public FileListing listFiles(String bucket, String prefix, String marker, int limit, String delimiter)
+            throws QiniuException {
+        StringMap map = new StringMap().put("bucket", bucket).putNotEmpty("marker", marker)
+                .putNotEmpty("prefix", prefix).putNotEmpty("delimiter", delimiter).putWhen("limit", limit, limit > 0);
+
+        String url = Config.RSF_HOST + "/list?" + map.formString();
+        Response r = get(url);
+        return r.jsonToObject(FileListing.class);
+    }
+
+    /**
+     * 获取指定空间、文件名的状态
+     *
+     * @param bucket
+     * @param key
+     * @return
+     * @throws QiniuException
+     */
+    public FileInfo stat(String bucket, String key) throws QiniuException {
+        Response r = rsGet("/stat/" + entry(bucket, key));
+        return r.jsonToObject(FileInfo.class);
+    }
+
+    /**
+     * 删除指定空间、文件名的文件
+     *
+     * @param bucket
+     * @param key
+     * @throws QiniuException
+     */
+    public void delete(String bucket, String key) throws QiniuException {
+        rsPost("/delete/" + entry(bucket, key));
+    }
+
+    /**
+     * 修改指定空间、文件的文件名
+     *
+     * @param bucket
+     * @param oldname
+     * @param newname
+     * @throws QiniuException
+     */
+    public void rename(String bucket, String oldname, String newname) throws QiniuException {
+        move(bucket, oldname, bucket, newname);
+    }
+
+    /**
+     * 复制文件。要求空间在同一账号下。
+     *
+     * @param from_bucket
+     * @param from_key
+     * @param to_bucket
+     * @param to_key
+     * @throws QiniuException
+     */
+    public void copy(String from_bucket, String from_key, String to_bucket, String to_key) throws QiniuException {
+        String from = entry(from_bucket, from_key);
+        String to = entry(to_bucket, to_key);
+        String path = "/copy/" + from + "/" + to;
+        rsPost(path);
+    }
+
+    /**
+     * 复制文件。要求空间在同一账号下, 可以添加force参数为true强行复制文件。
+     *
+     * @param from_bucket
+     * @param from_key
+     * @param to_bucket
+     * @param to_key
+     * @param force
+     * @throws QiniuException
+     */
+    public void copy(String from_bucket, String from_key, String to_bucket,
+                     String to_key, boolean force) throws QiniuException {
+        String from = entry(from_bucket, from_key);
+        String to = entry(to_bucket, to_key);
+        String path = "/copy/" + from + "/" + to + "/force/" + force;
+        rsPost(path);
+    }
+
+    /**
+     * 移动文件。要求空间在同一账号下。
+     *
+     * @param from_bucket
+     * @param from_key
+     * @param to_bucket
+     * @param to_key
+     * @throws QiniuException
+     */
+    public void move(String from_bucket, String from_key, String to_bucket, String to_key) throws QiniuException {
+        String from = entry(from_bucket, from_key);
+        String to = entry(to_bucket, to_key);
+        String path = "/move/" + from + "/" + to;
+        rsPost(path);
+    }
+
+    /**
+     * 移动文件。要求空间在同一账号下, 可以添加force参数为true强行移动文件。
+     *
+     * @param from_bucket
+     * @param from_key
+     * @param to_bucket
+     * @param to_key
+     * @param force
+     * @throws QiniuException
+     */
+    public void move(String from_bucket, String from_key, String to_bucket,
+                     String to_key, boolean force) throws QiniuException {
+        String from = entry(from_bucket, from_key);
+        String to = entry(to_bucket, to_key);
+        String path = "/move/" + from + "/" + to + "/force/" + force;
+        rsPost(path);
+    }
+
+    /**
+     * 修改完文件mimeTYpe
+     *
+     * @param bucket
+     * @param key
+     * @param mime
+     * @throws QiniuException
+     */
+    public void changeMime(String bucket, String key, String mime) throws QiniuException {
+        String resource = entry(bucket, key);
+        String encode_mime = UrlSafeBase64.encodeToString(mime);
+        String path = "/chgm/" + resource + "/mime/" + encode_mime;
+        rsPost(path);
+    }
+
+    /**
+     * 抓取指定地址的文件，已指定名称保存在指定空间。
+     * 要求指定url可访问。
+     * 大文件不建议使用此接口抓取。可先下载再上传。
+     *
+     * @param url
+     * @param bucket
+     * @throws QiniuException
+     */
+    public DefaultPutRet fetch(String url, String bucket) throws QiniuException {
+        return fetch(url, bucket, null);
+    }
+
+    /**
+     * 抓取指定地址的文件，已指定名称保存在指定空间。
+     * 要求指定url可访问。
+     * 大文件不建议使用此接口抓取。可先下载再上传。
+     *
+     * @param url
+     * @param bucket
+     * @param key
+     * @throws QiniuException
+     */
+    public DefaultPutRet fetch(String url, String bucket, String key) throws QiniuException {
+        String resource = UrlSafeBase64.encodeToString(url);
+        String to = entry(bucket, key, false);
+        String path = "/fetch/" + resource + "/to/" + to;
+        Response r = ioPost(path);
+        return r.jsonToObject(DefaultPutRet.class);
+    }
+
+    /**
+     * 对于设置了镜像存储的空间，从镜像源站抓取指定名称的资源并存储到该空间中。
+     * 如果该空间中已存在该名称的资源，则会将镜像源站的资源覆盖空间中相同名称的资源
+     *
+     * @param bucket
+     * @param key
+     * @throws QiniuException
+     */
+    public void prefetch(String bucket, String key) throws QiniuException {
+        String resource = entry(bucket, key);
+        String path = "/prefetch/" + resource;
+        ioPost(path);
+    }
+
+    /**
+     * 批量执行文件管理相关操作
+     *
+     * @param operations
+     * @return
+     * @throws QiniuException
+     * @see Batch
+     */
+    public Response batch(Batch operations) throws QiniuException {
+        return rsPost("/batch", operations.toBody());
+    }
+
+    private Response rsPost(String path, byte[] body) throws QiniuException {
+        String url = Config.RS_HOST + path;
+        return post(url, body);
+    }
+
+    private Response rsPost(String path) throws QiniuException {
+        return rsPost(path, null);
+    }
+
+    private Response rsGet(String path) throws QiniuException {
+        String url = Config.RS_HOST + path;
+        return get(url);
+    }
+
+    private Response ioPost(String path) throws QiniuException {
+        String url = Config.IO_HOST + path;
+        return post(url, null);
+    }
+
+    private Response get(String url) throws QiniuException {
+        StringMap headers = auth.authorization(url);
+        return client.get(url, headers);
+    }
+
+    private Response post(String url, byte[] body) throws QiniuException {
+        StringMap headers = auth.authorization(url, body, Client.FormMime);
+        return client.post(url, body, headers, Client.FormMime);
+    }
+
+    /**
+     * 文件管理操作指令
+     */
+    public static class Batch {
+        private ArrayList<String> ops;
+
+        public Batch() {
+            this.ops = new ArrayList<String>();
+        }
+
+        public Batch copy(String from_bucket, String from_key, String to_bucket, String to_key) {
+            String from = entry(from_bucket, from_key);
+            String to = entry(to_bucket, to_key);
+            ops.add("copy" + "/" + from + "/" + to);
+            return this;
+        }
+
+        public Batch rename(String from_bucket, String from_key, String to_key) {
+            return move(from_bucket, from_key, from_bucket, to_key);
+        }
+
+        public Batch move(String from_bucket, String from_key, String to_bucket, String to_key) {
+            String from = entry(from_bucket, from_key);
+            String to = entry(to_bucket, to_key);
+            ops.add("move" + "/" + from + "/" + to);
+            return this;
+        }
+
+        public Batch delete(String bucket, String... keys) {
+            for (String key : keys) {
+                ops.add("delete" + "/" + entry(bucket, key));
+            }
+            return this;
+        }
+
+        public Batch stat(String bucket, String... keys) {
+            for (String key : keys) {
+                ops.add("stat" + "/" + entry(bucket, key));
+            }
+            return this;
+        }
+
+        public byte[] toBody() {
+            String body = StringUtils.join(ops, "&op=", "op=");
+            return StringUtils.utf8Bytes(body);
+        }
+
+        public Batch merge(Batch batch) {
+            this.ops.addAll(batch.ops);
+            return this;
+        }
+    }
+
+    /**
+     * 获取文件列表迭代器
+     */
+    public class FileListIterator implements Iterator<FileInfo[]> {
+        private String marker = null;
+        private String bucket;
+        private String delimiter;
+        private int limit;
+        private String prefix;
+        private QiniuException exception = null;
+
+        public FileListIterator(String bucket, String prefix, int limit, String delimiter) {
+            if (limit <= 0) {
+                throw new IllegalArgumentException("limit must great than 0");
+            }
+            this.bucket = bucket;
+            this.prefix = prefix;
+            this.limit = limit;
+            this.delimiter = delimiter;
+        }
+
+        public QiniuException error() {
+            return exception;
+        }
+
+        @Override
+        public boolean hasNext() {
+            return exception == null && !"".equals(marker);
+        }
+
+        @Override
+        public FileInfo[] next() {
+            try {
+                FileListing f = listFiles(bucket, prefix, marker, limit, delimiter);
+                this.marker = f.marker == null ? "" : f.marker;
+                return f.items;
+            } catch (QiniuException e) {
+                this.exception = e;
+                return null;
+            }
+        }
+
+        @Override
+        public void remove() {
+            throw new UnsupportedOperationException("remove");
+        }
+    }
 }