Java code:

 private static <GOON extends Job> int maximumCost(List<GOON> jobs) {
     Deque<Job> running = new ArrayDeque<>();
     int cost = 0;
     int maxCost = 0;   
     
     for (Job job : jobs) {   
        running.push(job);
        cost += job.cost;
            
        //find jobs that have finished and remove their cost from current count
        for (Job jobToCheck : running) {
            if (job.begin > jobToCheck.end) {
                cost -= jobToCheck.cost;
                running.remove(jobToCheck);
            }
        }
         
        if (cost > maxCost) {
            maxCost = cost;
        }
     }
 
     return maxCost;
 }