package org.onap.dmaap.datarouter.node;
-import java.util.*;
+import java.util.HashSet;
+import java.util.Iterator;
/**
- * Manage a list of tasks to be executed when an event occurs.
- * This makes the following guarantees:
+ * Manage a list of tasks to be executed when an event occurs. This makes the following guarantees:
* <ul>
* <li>Tasks can be safely added and removed in the middle of a run.</li>
* <li>No task will be returned more than once during a run.</li>
* <li>No task will be returned when it is not, at that moment, in the list of tasks.</li>
* <li>At the moment when next() returns null, all tasks on the list have been returned during the run.</li>
- * <li>Initially and once next() returns null during a run, next() will continue to return null until startRun() is called.
+ * <li>Initially and once next() returns null during a run, next() will continue to return null until startRun() is
+ * called.
* </ul>
*/
-public class TaskList {
+class TaskList {
+
private Iterator<Runnable> runlist;
- private HashSet<Runnable> tasks = new HashSet<Runnable>();
+ private HashSet<Runnable> tasks = new HashSet<>();
private HashSet<Runnable> togo;
private HashSet<Runnable> sofar;
private HashSet<Runnable> added;
private HashSet<Runnable> removed;
- /**
- * Construct a new TaskList
- */
- public TaskList() {
- }
-
/**
* Start executing the sequence of tasks.
*/
- public synchronized void startRun() {
- sofar = new HashSet<Runnable>();
- added = new HashSet<Runnable>();
- removed = new HashSet<Runnable>();
- togo = new HashSet<Runnable>(tasks);
+ synchronized void startRun() {
+ sofar = new HashSet<>();
+ added = new HashSet<>();
+ removed = new HashSet<>();
+ togo = new HashSet<>(tasks);
runlist = togo.iterator();
}
/**
- * Get the next task to execute
+ * Get the next task to execute.
*/
- public synchronized Runnable next() {
+ synchronized Runnable next() {
while (runlist != null) {
if (runlist.hasNext()) {
Runnable task = runlist.next();
- if (removed.contains(task)) {
- continue;
+ if (addTaskToSoFar(task)) {
+ return task;
}
- if (sofar.contains(task)) {
- continue;
- }
- sofar.add(task);
- return (task);
}
- if (added.size() != 0) {
+ if (!added.isEmpty()) {
togo = added;
- added = new HashSet<Runnable>();
+ added = new HashSet<>();
removed.clear();
runlist = togo.iterator();
continue;
/**
* Add a task to the list of tasks to run whenever the event occurs.
*/
- public synchronized void addTask(Runnable task) {
+ synchronized void addTask(Runnable task) {
if (runlist != null) {
added.add(task);
removed.remove(task);
/**
* Remove a task from the list of tasks to run whenever the event occurs.
*/
- public synchronized void removeTask(Runnable task) {
+ synchronized void removeTask(Runnable task) {
if (runlist != null) {
removed.add(task);
added.remove(task);
}
tasks.remove(task);
}
+
+ private boolean addTaskToSoFar(Runnable task) {
+ if (removed.contains(task)) {
+ return false;
+ }
+ if (sofar.contains(task)) {
+ return false;
+ }
+ sofar.add(task);
+ return true;
+ }
}