Question

Like so?

abstract public class BaseTask extends Runnable {
    public BaseTask(ParamA aParam) {
         // do something with aParam
         StaticExecutorService.submit(this);
    }
}

public class AbcTask extends BaseTask {
    public ABC(ParamA aParam, ParamB bParam) {
        super(aParam);
    }
    @Override
    public void run() {

    }
}

The class can then just be created and queued for execution by doing a

new AbcTask();

1. I’m not sure if this is ok because maybe it is still being constructed when ExecutorService decides to execute AbcTask?

2. If you don’t recommend this for whatever reason, please state and elaborate.

Thanks

Answer 1

In your example it will probably work but as the call to super() has to be the first in child classes of BaseTask this means that the constructor won’t be able to perform any operation before the submission of the task.

From you sample, the second parameter cannot be used since the task will be submitted before you can assign it to an attribute.

If we consider the following code:

public class MyTask extends BaseTask {
    public ABC(ParamA aParam, String name) {
        super(aParam);
        this.name = name == null ? "Default Value" : name;
    }
    @Override
    public void run() {
         System.out.println("Name length: "+ name.length());
    }
}

Since run() can be called before the assignment of this.name the System.out line can end in NullPointerException