java - Interview: How to ensure that a thread runs after another?

Question

There are thread T1, T2 and T3, how can we ensure that thread T2 run after T1 and thread T3 run after T2?

This question was asked in my interview. I didn't answer. Please explain in detail.

Answer 1

This would be the simplest, dumbest approach:

final Thread t1 = new Thread(new T1()); // assume T1 is a Runnable
t1.start();
t1.join();
final Thread t2 = new Thread(new T2());
t2.start();
t2.join();
final Thread t3 = new Thread(new T3());
t3.start();
t3.join();