what does particleEmitter.start() method do in particle emitter class?

Question

whether I put start() method or not my particle emitter runs the same way, So what is the use of start() method.

Answer 1

If you look at the source code of ParticleEffect class and then look at the start method, you will see this -

public void start () {
    for (int i = 0, n = emitters.size; i < n; i++)
        emitters.get(i).start();
}

Basically, this means it is going through all the emitters and calling ParticleEmitter#start method.

Now let's look into the start method of ParticleEmitter.

public void start () {
    firstUpdate = true;
    allowCompletion = false;
    restart();
}

Basically from the method, you can see that its setting the firstUpdate boolean to true which means "this is the first update" i.e. we will be doing something for the first time (look into the source code to see where the boolean is used)

The next line, it is setting allowCompletion to false which means, if the emitter was already in progress, don't let it complete (Check source code to see where the boolean is used)

The final call is to restart() which is self-explanatory (restarting this emitter if it was already running.)

I hope that helped.