public void determineExecutionPlan() { List<TaskInfo> nodeQueue = CollectionUtils.collect( new ArrayList<Task>(entryTasks), new Transformer<TaskInfo, Task>() { public TaskInfo transform(Task original) { return graph.getNode(original); } }); Set<TaskInfo> visitingNodes = new HashSet<TaskInfo>(); while (!nodeQueue.isEmpty()) { TaskInfo taskNode = nodeQueue.get(0); boolean filtered = !filter.isSatisfiedBy(taskNode.getTask()); if (filtered) { taskNode.setRequired(false); } if (!taskNode.getRequired() || executionPlan.containsKey(taskNode.getTask())) { nodeQueue.remove(0); continue; } if (visitingNodes.add(taskNode)) { // Have not seen this task before - add its dependencies to the head of the queue and leave // this // task in the queue ArrayList<TaskInfo> dependsOnTasks = new ArrayList<TaskInfo>(); addAllReversed(dependsOnTasks, taskNode.getHardSuccessors()); addAllReversed(dependsOnTasks, taskNode.getSoftSuccessors()); for (TaskInfo dependsOnTask : dependsOnTasks) { if (visitingNodes.contains(dependsOnTask)) { throw new CircularReferenceException( String.format( "Circular dependency between tasks. Cycle includes [%s, %s].", taskNode.getTask(), dependsOnTask.getTask())); } nodeQueue.add(0, dependsOnTask); } } else { // Have visited this task's dependencies - add it to the end of the plan nodeQueue.remove(0); visitingNodes.remove(taskNode); executionPlan.put(taskNode.getTask(), taskNode); } } }