diff --git a/src/main/java/com/github/stephengold/joltjni/std/DefaultRandomEngine.java b/src/main/java/com/github/stephengold/joltjni/std/DefaultRandomEngine.java
index 352d8d41..da2821e4 100644
--- a/src/main/java/com/github/stephengold/joltjni/std/DefaultRandomEngine.java
+++ b/src/main/java/com/github/stephengold/joltjni/std/DefaultRandomEngine.java
@@ -1,5 +1,5 @@
 /*
-Copyright (c) 2024 Stephen Gold
+Copyright (c) 2024-2025 Stephen Gold
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -32,7 +32,9 @@ of this software and associated documentation files (the "Software"), to deal
  *
  * @author Stephen Gold sgold@sonic.net
  */
-public class DefaultRandomEngine extends JoltPhysicsObject {
+public class DefaultRandomEngine
+        extends JoltPhysicsObject
+        implements RandomNumberEngine {
     // *************************************************************************
     // constructors
 
@@ -54,13 +56,14 @@ public DefaultRandomEngine(int seed) {
         setVirtualAddress(generatorVa, () -> free(generatorVa));
     }
     // *************************************************************************
-    // new methods exposed
+    // RandomEngine methods
 
     /**
      * Return the next integer in the sequence.
      *
      * @return an integer value
      */
+    @Override
     public int nextInt() {
         long generatorVa = va();
         int result = nextInt(generatorVa);
diff --git a/src/main/java/com/github/stephengold/joltjni/std/RandomNumberEngine.java b/src/main/java/com/github/stephengold/joltjni/std/RandomNumberEngine.java
new file mode 100644
index 00000000..1052a09a
--- /dev/null
+++ b/src/main/java/com/github/stephengold/joltjni/std/RandomNumberEngine.java
@@ -0,0 +1,41 @@
+/*
+Copyright (c) 2025 Stephen Gold
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+ */
+package com.github.stephengold.joltjni.std;
+
+import com.github.stephengold.joltjni.readonly.ConstJoltPhysicsObject;
+
+/**
+ * Interface to a pseudo-random number engine.
+ *
+ * @author Stephen Gold sgold@sonic.net
+ */
+public interface RandomNumberEngine extends ConstJoltPhysicsObject {
+    // *************************************************************************
+    // new methods exposed
+
+    /**
+     * Return the next integer in the sequence.
+     *
+     * @return an integer value
+     */
+    int nextInt();
+}