diff --git a/README.md b/README.md
index 57e30f23..d9664bff 100644
--- a/README.md
+++ b/README.md
@@ -16,10 +16,11 @@ A general programming library in Java/Android. It's easy to learn and simple to
 [Maps](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Maps_view.html), 
 [DateUtil](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/DateUtil_view.html), 
 [IOUtil](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/IOUtil_view.html), 
+[f](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/f_view.html), 
 [Indexed](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Indexed_view.html), 
 [If](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/If_view.html), 
 [Try](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Try_view.html), 
-[Synchronzed](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Synchronzed_view.html), 
+[Synchronized](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Synchronzed_view.html), 
 [Retry](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Retry_view.html), 
 [Multiset](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Multiset_view.html), 
 [Multimap](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Multimap_view.html),
@@ -57,8 +58,7 @@ A general programming library in Java/Android. It's easy to learn and simple to
 [HttpClient](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/HttpClient_view.html), 
 [OkHttpRequest](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/OkHttpRequest_view.html), 
 [Profiler](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/Profiler_view.html), 
-[CodeGenerator](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/CodeGenerator_view.html), 
-[f](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/f_view.html)...
+[CodeGenerator](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/CodeGenerator_view.html)...
 
 * Primitive Mutable: 
 [MutableBoolean](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/MutableBoolean_view.html), 
@@ -182,33 +182,33 @@ A general programming library in Java/Android. It's easy to learn and simple to
 [RemoteExecutor](https://cdn.rawgit.com/landawn/AbacusUtil/master/docs/RemoteExecutor_view.html).
 
 * More: 
-[Charsets](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Charsets.html),
-[Ascii](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Ascii.html),
-[CalendarUnit](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/CalendarUnit.html),
-[NamingPolicy](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/NamingPolicy.html), 
-[Properties](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Properties.html),
-[PropertiesUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/PropertiesUtil.html),
-[Wrapper](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Wrapper.html),
-[ArrayHashSet](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/ArrayHashSet.html),
-[ArrayHashMap](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/ArrayHashMap.html),
-[ClassUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/ClassUtil.html),
-[EscapeUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/EscapeUtil.html),
-[RegExUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/RegExUtil.html),
-[FilenameUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/FilenameUtil.html),
-[AWSJSONUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/AWSJSONUtil.html),
-[AddrUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/AddrUtil.html),
-[WSSecurityUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/WSSecurityUtil.html),
-[EmailUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/EmailUtil.html),
-[IEEE754rUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/IEEE754rUtil.html),
-[Index](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Index.html),
-[Median](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Median.html),
-[f](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/f.html),
-[Iterables](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Iterables.html),
-[Matth](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Matth.html), 
-[SafeInitializer](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/SafeInitializer.html),
-[Stopwatch](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Stopwatch.html),
-[RateLimiter](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/RateLimiter.html),
-[Traverser](https://static.javadoc.io/com.landawn/abacus-util/1.5.4/com/landawn/abacus/util/Traverser.html)(from Apache commons, Google Guava...) ...
+[Charsets](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Charsets.html),
+[Ascii](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Ascii.html),
+[CalendarUnit](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/CalendarUnit.html),
+[NamingPolicy](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/NamingPolicy.html), 
+[Properties](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Properties.html),
+[PropertiesUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/PropertiesUtil.html),
+[Wrapper](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Wrapper.html),
+[ArrayHashSet](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/ArrayHashSet.html),
+[ArrayHashMap](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/ArrayHashMap.html),
+[ClassUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/ClassUtil.html),
+[EscapeUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/EscapeUtil.html),
+[RegExUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/RegExUtil.html),
+[FilenameUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/FilenameUtil.html),
+[AWSJSONUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/AWSJSONUtil.html),
+[AddrUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/AddrUtil.html),
+[WSSecurityUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/WSSecurityUtil.html),
+[EmailUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/EmailUtil.html),
+[IEEE754rUtil](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/IEEE754rUtil.html),
+[Index](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Index.html),
+[Median](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Median.html),
+[f](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/f.html),
+[Iterables](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Iterables.html),
+[Matth](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Matth.html), 
+[SafeInitializer](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/SafeInitializer.html),
+[Stopwatch](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Stopwatch.html),
+[RateLimiter](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/RateLimiter.html),
+[Traverser](https://static.javadoc.io/com.landawn/abacus-util/1.5.5/com/landawn/abacus/util/Traverser.html)(from Apache commons, Google Guava...) ...
 
 
 ## Download/Installation & [Changes](https://github.com/landawn/AbacusUtil/blob/master/CHANGES.md):
@@ -218,22 +218,22 @@ A general programming library in Java/Android. It's easy to learn and simple to
 * Gradle:
 ```gradle
 // JDK 1.8 or above:
-compile 'com.landawn:abacus-util:1.5.4'
+compile 'com.landawn:abacus-util:1.5.5'
 
 // JDK 1.7:
-compile 'com.landawn:abacus-util-jdk7:1.5.4'
+compile 'com.landawn:abacus-util-jdk7:1.5.5'
 
 // Android (Java 1.7):
-compile 'abacus-android-jdk7:1.5.4'
+compile 'abacus-android-jdk7:1.5.5'
 
 // Android-SE (Java 1.7) - small edition without Stream/Matrix/Sheet/...:
-compile 'abacus-android-se-jdk7:1.5.4'
+compile 'abacus-android-se-jdk7:1.5.5'
 
 // Android (Java 1.8 or above):
-compile 'com.landawn:abacus-android:1.5.4'
+compile 'com.landawn:abacus-android:1.5.5'
 
 // Android-SE (Java 1.8 or above) - small edition without Stream/Matrix/Sheet/...:
-compile 'com.landawn:abacus-android-se:1.5.4'
+compile 'com.landawn:abacus-android-se:1.5.5'
 ```
 ### Functional Programming:
 (It's very important to learn Lambdas and Stream APIs in Java 8 to get the best user experiences with the APIs provided in AbacusUtil)
diff --git a/docs/N.gif b/docs/N.gif
index 3a72cd88..23e91a12 100644
Binary files a/docs/N.gif and b/docs/N.gif differ
diff --git a/docs/Timed.gif b/docs/Timed.gif
new file mode 100644
index 00000000..2009185e
Binary files /dev/null and b/docs/Timed.gif differ
diff --git a/lib/abacus-android-1.5.4.jar b/lib/abacus-android-1.5.5.jar
similarity index 70%
rename from lib/abacus-android-1.5.4.jar
rename to lib/abacus-android-1.5.5.jar
index 10016b4f..79db7b87 100644
Binary files a/lib/abacus-android-1.5.4.jar and b/lib/abacus-android-1.5.5.jar differ
diff --git a/lib/abacus-android-jdk7-1.5.4.jar b/lib/abacus-android-jdk7-1.5.5.jar
similarity index 84%
rename from lib/abacus-android-jdk7-1.5.4.jar
rename to lib/abacus-android-jdk7-1.5.5.jar
index a5d482e2..e3e0ed36 100644
Binary files a/lib/abacus-android-jdk7-1.5.4.jar and b/lib/abacus-android-jdk7-1.5.5.jar differ
diff --git a/lib/abacus-android-se-1.5.4.jar b/lib/abacus-android-se-1.5.5.jar
similarity index 79%
rename from lib/abacus-android-se-1.5.4.jar
rename to lib/abacus-android-se-1.5.5.jar
index b37b2cc1..956696d8 100644
Binary files a/lib/abacus-android-se-1.5.4.jar and b/lib/abacus-android-se-1.5.5.jar differ
diff --git a/lib/abacus-android-se-jdk7-1.5.4.jar b/lib/abacus-android-se-jdk7-1.5.5.jar
similarity index 81%
rename from lib/abacus-android-se-jdk7-1.5.4.jar
rename to lib/abacus-android-se-jdk7-1.5.5.jar
index 89ab3210..a8600444 100644
Binary files a/lib/abacus-android-se-jdk7-1.5.4.jar and b/lib/abacus-android-se-jdk7-1.5.5.jar differ