Is singleton thread-safe? vs Object?

Answer

Is Kotlin object thread-safe?

Yes. The initialization of an object singleton in Kotlin is thread-safe. It relies on the JVM's static initialization locking mechanism.

vs Object (Java)

In Java, you often had to write:

Copy codepublic class Singleton {
    private static Singleton instance;
    public static synchronized Singleton getInstance() { ... }
}

Kotlin handles this automatically.

However, the properties inside the object are NOT automatically thread-safe. If you have a mutable var inside an object, you still need to synchronize access to it if multiple threads modify it.