question: public void push ( ) { Deque < TaskContext > stack = contextStacks . get ( ) ; if ( stack == null ) { stack = new LinkedList < > ( ) ; contextStacks . set ( stack ) ; final Thread currentThread = Thread . currentThread ( ) ; synchronized ( contextStacksMap ) { contextStacksMap . put ( currentThread , stack ) ; } } stack . addLast ( this ) ; }
target:  Adds this execution context to the top of the context stack for the current thread.