Sequencing in multi-threading can be achieved by different means but
you can simply use join() method of thread class to start a thread when another one is
finished its execution.
To ensure three threads execute you need to start the last one
first e.g. T3 and then call join methods in reverse order e.g. T3 calls T2. join, and T2
calls T1.join, this ways T1 will finish first and T3 will finish last.