diff --git a/packages/react-native/ReactAndroid/api/ReactAndroid.api b/packages/react-native/ReactAndroid/api/ReactAndroid.api
index 0c037160bd7b6f..585734f3b5a1f9 100644
--- a/packages/react-native/ReactAndroid/api/ReactAndroid.api
+++ b/packages/react-native/ReactAndroid/api/ReactAndroid.api
@@ -1687,7 +1687,7 @@ public abstract interface class com/facebook/react/common/HasJavascriptException
 public class com/facebook/react/common/JavascriptException : java/lang/RuntimeException, com/facebook/react/common/HasJavascriptExceptionMetadata {
 	public fun <init> (Ljava/lang/String;)V
 	public fun getExtraDataAsJson ()Ljava/lang/String;
-	public fun setExtraDataAsJson (Ljava/lang/String;)Lcom/facebook/react/common/JavascriptException;
+	public final fun setExtraDataAsJson (Ljava/lang/String;)Lcom/facebook/react/common/JavascriptException;
 }
 
 public final class com/facebook/react/common/LifecycleState : java/lang/Enum {
@@ -1771,11 +1771,11 @@ public abstract interface class com/facebook/react/common/SurfaceDelegateFactory
 	public abstract fun createSurfaceDelegate (Ljava/lang/String;)Lcom/facebook/react/common/SurfaceDelegate;
 }
 
-public class com/facebook/react/common/SystemClock {
-	public fun <init> ()V
-	public static fun currentTimeMillis ()J
-	public static fun nanoTime ()J
-	public static fun uptimeMillis ()J
+public final class com/facebook/react/common/SystemClock {
+	public static final field INSTANCE Lcom/facebook/react/common/SystemClock;
+	public static final fun currentTimeMillis ()J
+	public static final fun nanoTime ()J
+	public static final fun uptimeMillis ()J
 }
 
 public abstract interface annotation class com/facebook/react/common/annotations/DeprecatedInNewArchitecture : java/lang/annotation/Annotation {
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.java
deleted file mode 100644
index e8caa1c6bff93d..00000000000000
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.java
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.react.common;
-
-import com.facebook.infer.annotation.Nullsafe;
-import com.facebook.proguard.annotations.DoNotStrip;
-import javax.annotation.Nullable;
-
-/**
- * A JS exception that was propagated to native. In debug mode, these exceptions are normally shown
- * to developers in a redbox.
- */
-@Nullsafe(Nullsafe.Mode.LOCAL)
-@DoNotStrip
-public class JavascriptException extends RuntimeException
-    implements HasJavascriptExceptionMetadata {
-
-  private @Nullable String extraDataAsJson;
-
-  public JavascriptException(String jsStackTrace) {
-    super(jsStackTrace);
-  }
-
-  public @Nullable String getExtraDataAsJson() {
-    return extraDataAsJson;
-  }
-
-  public JavascriptException setExtraDataAsJson(@Nullable String extraDataAsJson) {
-    this.extraDataAsJson = extraDataAsJson;
-    return this;
-  }
-}
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.kt b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.kt
new file mode 100644
index 00000000000000..df15d4567f924b
--- /dev/null
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/JavascriptException.kt
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.common
+
+import com.facebook.proguard.annotations.DoNotStrip
+
+/**
+ * A JS exception that was propagated to native. In debug mode, these exceptions are normally shown
+ * to developers in a redbox.
+ */
+@DoNotStrip
+public open class JavascriptException(jsStackTrace: String) :
+    RuntimeException(jsStackTrace), HasJavascriptExceptionMetadata {
+  private var extraDataAsJson: String? = null
+
+  override fun getExtraDataAsJson(): String? = extraDataAsJson
+
+  public fun setExtraDataAsJson(extraDataAsJson: String?): JavascriptException {
+    this.extraDataAsJson = extraDataAsJson
+    return this
+  }
+}
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.java
deleted file mode 100644
index 53aada5deb7b95..00000000000000
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.java
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.react.common;
-
-import com.facebook.infer.annotation.Nullsafe;
-
-/**
- * Detour for System.currentTimeMillis and System.nanoTime calls so that they can be mocked out in
- * tests.
- */
-@Nullsafe(Nullsafe.Mode.LOCAL)
-public class SystemClock {
-
-  public static long currentTimeMillis() {
-    return System.currentTimeMillis();
-  }
-
-  public static long nanoTime() {
-    return System.nanoTime();
-  }
-
-  public static long uptimeMillis() {
-    return android.os.SystemClock.uptimeMillis();
-  }
-}
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.kt b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.kt
new file mode 100644
index 00000000000000..049c9ab927a0e4
--- /dev/null
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SystemClock.kt
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.common
+
+import android.os.SystemClock
+
+/**
+ * Detour for System.currentTimeMillis and System.nanoTime calls so that they can be mocked out in
+ * tests.
+ */
+public object SystemClock {
+  @JvmStatic public fun currentTimeMillis(): Long = System.currentTimeMillis()
+
+  @JvmStatic public fun nanoTime(): Long = System.nanoTime()
+
+  @JvmStatic public fun uptimeMillis(): Long = SystemClock.uptimeMillis()
+}