Review code and give me best Java code solution. Threads/Concurrencies/Locks

I have some problem with threading,concurreny and locks. It is only in a class.
The logic-> to stream prices with websocket and compare market price with my price, if true -> send an order to the exchange . While I am sending buy order to exchange, I want to restart/update my socket/thread and remove all other waiting threads.

I have tried Synchronized,locks,boolean var, thread.join

please se attached files