Is it wrong to do runnable.run()?

Question

I am fairly new to the concept of multithreading and there is an aspect which is not clear to me.

There are two ways to create and run a thread:

Extend a Thread class and start() the thread.
Create a Runnable object, pass it to a Thread constructor and start() the thread.

And this blog post states that we always should start a thread using a start() or so was my impression of it.

But in one of the answers here you could see how a person is using runnable.run(). It gives me an impression of somewhat wrong practice.

Is it normal? Should it be avoided? You can be explicit in your answer, but any suggestions would be appreciated.

`run` is just a method declared in the `Runnable` interface. There's no magic. — Sotirios Delimanolis, Apr 04 '14 at 03:07
ok. Should I run the runnable? Or start a Thread. Isn't runnable interface designed specifically to be used with a thread? — user3081519, Apr 04 '14 at 03:08
Sure, primarily. And internally, `Thread` simply does call `run` on the `Runnable` instance you pass it. There's nothing preventing you from doing the same. But note, that that alone does not start a thread. — Sotirios Delimanolis, Apr 04 '14 at 03:09
Aha... So if I enclose some statements in runnable and do .run() it simply means that I execute these statements sequentially, like I would otherwise? — user3081519, Apr 04 '14 at 03:17
That's exactly right. The `Thread` class is the one doing the thread magic. — Sotirios Delimanolis, Apr 04 '14 at 03:17
The `run` method simply does the work. The `Thread` class actually represents the thread which executes the `run` method and burdens itself with the work defined by `run`. — Martin Tuskevicius, Apr 04 '14 at 04:28

score 5 · Accepted Answer · answered Apr 04 '14 at 03:19

They're just different things. run() executes the Runnable in the current thread. Calling start(), on the other hand, causes the Runnable to run in the new thread.

The tutorial points it out as a pitfall. You went through all that trouble to make a thread, so if you go on to run it in the current thread instead, then it's likely a mistake.

Is it wrong to do runnable.run()?

1 Answers1