I added Folia support without breaking previous versions for Spigot.

I removed the Bukkit Scheduler implementation to use the Concurrent Executors implementation which is much more maintainable than using an implementation that requires to use another package for Folia like here MilkBowl#915

plugin.yml

@@ -4,6 +4,7 @@ description: ${project.description}
 authors: [cereal, Sleaker, mung3r]
 website: ${project.url}
 api-version: 1.13
+folia-supported: true
 
 main: ${mainClass}
 load: startup

src/net/milkbowl/vault/Vault.java

@@ -21,6 +21,8 @@
 import java.net.URLConnection;
 import java.util.Collection;
 import java.util.concurrent.Callable;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 import net.milkbowl.vault.chat.Chat;
@@ -76,6 +78,8 @@
 import org.json.simple.JSONObject;
 import org.json.simple.JSONValue;
 
+import java.util.concurrent.Executors;
+
 import net.milkbowl.vault.chat.plugins.Chat_TotalPermissions;
 
 public class Vault extends JavaPlugin {
@@ -89,12 +93,15 @@ public class Vault extends JavaPlugin {
     private String currentVersionTitle = "";
     private ServicesManager sm;
     private Vault plugin;
+    private ScheduledExecutorService asyncTaskTimer;
 
     @Override
     public void onDisable() {
         // Remove all Service Registrations
         getServer().getServicesManager().unregisterAll(this);
-        Bukkit.getScheduler().cancelTasks(this);
+        if (asyncTaskTimer != null) {
+            asyncTaskTimer.shutdownNow();
+        }
     }
 
     @Override
@@ -115,44 +122,34 @@ public void onEnable() {
         getCommand("vault-info").setExecutor(this);
         getCommand("vault-convert").setExecutor(this);
         getServer().getPluginManager().registerEvents(new VaultListener(), this);
+        asyncTaskTimer = Executors.newScheduledThreadPool(1);
         // Schedule to check the version every 30 minutes for an update. This is to update the most recent 
         // version so if an admin reconnects they will be warned about newer versions.
-        this.getServer().getScheduler().runTask(this, new Runnable() {
-
-            @Override
-            public void run() {
-                // Programmatically set the default permission value cause Bukkit doesn't handle plugin.yml properly for Load order STARTUP plugins
-                org.bukkit.permissions.Permission perm = getServer().getPluginManager().getPermission("vault.update");
-                if (perm == null)
-                {
-                    perm = new org.bukkit.permissions.Permission("vault.update");
-                    perm.setDefault(PermissionDefault.OP);
-                    plugin.getServer().getPluginManager().addPermission(perm);
-                }
-                perm.setDescription("Allows a user or the console to check for vault updates");
-
-                getServer().getScheduler().runTaskTimerAsynchronously(plugin, new Runnable() {
-
-                    @Override
-                    public void run() {
-                        if (getServer().getConsoleSender().hasPermission("vault.update") && getConfig().getBoolean("update-check", true)) {
-                            try {
-                            	log.info("Checking for Updates ... ");
-                                newVersion = updateCheck(currentVersion);
-                                if (newVersion > currentVersion) {
-                                    log.warning("Stable Version: " + newVersionTitle + " is out!" + " You are still running version: " + currentVersionTitle);
-                                    log.warning("Update at: https://dev.bukkit.org/projects/vault");
-                                } else if (currentVersion > newVersion) {
-                                    log.info("Stable Version: " + newVersionTitle + " | Current Version: " + currentVersionTitle);
-                                }
-                            } catch (Exception e) {
-                                // ignore exceptions
-                            }
+        Executors.newSingleThreadExecutor().execute(() -> {
+            org.bukkit.permissions.Permission perm = getServer().getPluginManager().getPermission("vault.update");
+            if (perm == null)
+            {
+                perm = new org.bukkit.permissions.Permission("vault.update");
+                perm.setDefault(PermissionDefault.OP);
+                plugin.getServer().getPluginManager().addPermission(perm);
+            }
+            perm.setDescription("Allows a user or the console to check for vault updates");
+            asyncTaskTimer.scheduleAtFixedRate(() -> {
+                if (getServer().getConsoleSender().hasPermission("vault.update") && getConfig().getBoolean("update-check", true)) {
+                    try {
+                        log.info("Checking for Updates ... ");
+                        newVersion = updateCheck(currentVersion);
+                        if (newVersion > currentVersion) {
+                            log.warning("Stable Version: " + newVersionTitle + " is out!" + " You are still running version: " + currentVersionTitle);
+                            log.warning("Update at: https://dev.bukkit.org/projects/vault");
+                        } else if (currentVersion > newVersion) {
+                            log.info("Stable Version: " + newVersionTitle + " | Current Version: " + currentVersionTitle);
                         }
+                    } catch (Exception e) {
+                        // ignore exceptions
                     }
-                }, 0, 432000);
-
-            }
+                }
+            }, 0, 21600, TimeUnit.SECONDS);
         });
 
         // Load up the Plugin metrics