How to design an execution engine for a sequence of tasks

Question

I am trying to code a problem in Java where I have to execute a bunch of tasks.

Problem

Execute a job which consists of multiple tasks and thos

Answer 1

Your problem seems to be a modified version of the Observer Pattern. The solution below is more general than as it allows dependency on a list of tasks to proceed.

Create a class Task as follows:

class Task{
List partialCompletionSuccessors;//List of tasks dependent on the partial completeion of this Task
List fullCompletetionSuccessors;//List of tasks dependent on the full completeion of this Task

List partialCompletionPredeccessor;//List of tasks that this task depends on their partial completion to start
List fullCompletetionPredeccessor;//List of tasks that this task depends on their full completion to start


private void notifySuccessorsOfPartialCompletion(){
    for(Task task: partialCompletionSuccessors){
           task.notifyOfPartialCompletion(this);
    }

}

private void notifySuccessorsOfFullCompletion(){
    for(Task task: fullCompletetionSuccessors){
           task.notifyOfPartialCompletion(this);
    }

}

private tryToProcceed(){
 if(partialCompletionPredeccessor.size() == 0 && fullCompletetionPredeccessor.size()==0 ){
     //Start the following task...
      ....
     //When this task partially completes
    notifySuccessorsOfPartialCompletion();

      //When this task fully completes
      notifySuccessorsOfFullCompletion();

  }

}


public void notifyOfPartialCompletion(Task task){// A method to notify the following task that a predeccessor task has partially completed
      partialCompletionPredeccessor.remove(task);
      tryToProcceed();

}

public void notifyOfFullCompletion(Task task){// A method to notify the following task that a predeccessor task has partially completed
      fullCompletetionPredeccessor.remove(task);
      tryToProcceed();

}

}