Simplified by using instance methods

core/src/main/java/hudson/diagnosis/NullIdDescriptorMonitor.java

@@ -60,7 +60,8 @@ public class NullIdDescriptorMonitor extends AdministrativeMonitor {
         return Collections.unmodifiableList(problems);
     }
 
-    private void verify() {
+    @Initializer(after=EXTENSIONS_AUGMENTED)
+    public void verify() {
         Jenkins h = Jenkins.getInstance();
         for (Descriptor d : h.getExtensionList(Descriptor.class)) {
             PluginWrapper p = h.getPluginManager().whichPlugin(d.getClass());
@@ -81,10 +82,5 @@ public class NullIdDescriptorMonitor extends AdministrativeMonitor {
         }
     }
 
-    @Initializer(after=EXTENSIONS_AUGMENTED)
-    public static void verifyId() {
-        AdministrativeMonitor.all().get(NullIdDescriptorMonitor.class).verify();
-    }
-
     private static final Logger LOGGER = Logger.getLogger(NullIdDescriptorMonitor.class.getName());
 }

core/src/main/java/jenkins/model/Uptime.java

@@ -27,7 +27,7 @@ public class Uptime {
     }
 
     @Initializer(after=InitMilestone.JOB_LOADED)
-    public static void init() {
-        ExtensionList.lookup(Uptime.class).get(0).startTime = System.currentTimeMillis();
+    public void init() {
+        startTime = System.currentTimeMillis();
     }
 }

core/src/main/java/jenkins/security/RekeySecretAdminMonitor.java

@@ -113,13 +113,11 @@ public class RekeySecretAdminMonitor extends AsynchronousAdministrativeMonitor i
 
     @Initializer(fatal=false,after=InitMilestone.PLUGINS_STARTED,before=InitMilestone.EXTENSIONS_AUGMENTED)
     // as early as possible, but this needs to be late enough that the ConfidentialStore is available
-    public static void scanOnReboot() throws InterruptedException, IOException, GeneralSecurityException {
-        RekeySecretAdminMonitor m = new RekeySecretAdminMonitor();  // throw-away instance
-
-        FileBoolean flag = m.scanOnBoot;
+    public void scanOnReboot() throws InterruptedException, IOException, GeneralSecurityException {
+        FileBoolean flag = scanOnBoot;
         if (flag.isOn()) {
             flag.off();
-            m.start(false).join();
+            start(false).join();
             // block the boot until the rewrite process is complete
             // don't let the failure in RekeyThread block Jenkins boot.
         }