8364461: JFR: Default constructor may not be first in setting control

src/jdk.jfr/share/classes/jdk/jfr/internal/EventControl.java

@@ -285,20 +285,25 @@ private void defineSetting(Class<? extends SettingControl> settingsClass, Method
 
     private SettingControl instantiateSettingControl(Class<? extends SettingControl> settingControlClass) throws IllegalAccessException, InstantiationException {
         SecuritySupport.makeVisibleToJFR(settingControlClass);
-        final Constructor<?> cc;
-        try {
-            cc = settingControlClass.getDeclaredConstructors()[0];
-        } catch (Exception e) {
-            throw (Error) new InternalError("Could not get constructor for " + settingControlClass.getName()).initCause(e);
-        }
-        cc.setAccessible(true);
         try {
+            Constructor<?> cc = findDefaultConstructor(settingControlClass);
+            cc.setAccessible(true);
             return (SettingControl) cc.newInstance();
         } catch (IllegalArgumentException | InvocationTargetException e) {
             throw new InternalError("Could not instantiate setting for class " + settingControlClass.getName());
         }
     }
 
+    private Constructor<?> findDefaultConstructor(Class<? extends SettingControl> settingControlClass) {
+        for (Constructor<?> c : settingControlClass.getDeclaredConstructors()) {
+            if (c.getParameterCount() == 0) {
+                return c;
+            }
+        }
+        // Programming error by user, fail fast
+        throw new InstantiationError("Could not find default constructor for " + settingControlClass.getName());
+    }
+
     private static Control defineEnabled(PlatformEventType type) {
         // Java events are enabled by default,
         // JVM events are not, maybe they should be? Would lower learning curve

test/jdk/jdk/jfr/api/settings/RegExpControl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,6 +31,14 @@
 public final class RegExpControl extends SettingControl {
     private Pattern pattern = Pattern.compile(".*");
 
+    // Purpose of this constructor is to ensure that the correct
+    // constructor is picked when the event class is registered
+    public RegExpControl(String dummy) {
+    }
+
+    public RegExpControl() {
+    }
+
     public void setValue(String value) {
         this.pattern = Pattern.compile(value);
     }