Synchronization of new data with previous data
Coding Conventions

First of all: You should follow common naming conventions for Java.  It makes it harder to read your code if you don't -- or to put it differently: It is easier to help if the code does follow common conventions.  Maybe have a look at Google's Java Style or at least:


write methods in lowerCamelCase style and
classes in UpperCamelCase style.


Furthermore it would be good to provide a compilable minimal example. 

Threadsafe List

From what I understood you want to have a list which is capable of being accessed and modified from multiple threads.  If so, you may have a look at this stackoverflow discussion.  

Java Concurrency

Some general things: 


You don't need to instantiate an object for your synchronized blocks.  If you do not specify an object, the current object is used.  That should be sufficient for your use cases.
Don't start a thread directly.  Rather use an ExecutorService instead.
Don't subclass Thread, but rather use a Runnable (also see here).
Very good book on the whole topic: Java Concurrency in Practice.