How Can I Serialize a Lambda Expression in Java Without Creating a Dummy Interface?

Serializing a Lambda: A Solution Without Dummy Interfaces

In Java programming, it's not uncommon to encounter scenarios where you need to serialize lambda expressions. However, attempts to directly serialize a lambda often result in a NotSerializableException.

Consider the following example:

public static void main(String[] args) throws Exception {
    File file = Files.createTempFile("lambda", "ser").toFile();
    try (ObjectOutput oo = new ObjectOutputStream(new FileOutputStream(file))) {
        Runnable r = () -> System.out.println("Can I be serialized?");
        oo.writeObject(r);
    }

    try (ObjectInput oi = new ObjectInputStream(new FileInputStream(file))) {
        Runnable r = (Runnable) oi.readObject();
        r.run();
    }
}

In this case, serializing the lambda throws a NotSerializableException.

To overcome this challenge, Java 8 introduces a clever solution: casting an object to an intersection of types. By adding multiple bounds to the lambda's type, you can elegantly make it serializable:

Runnable r = (Runnable & Serializable)() -> System.out.println("Serializable!");

This technique allows the lambda to automatically inherit the Serializable interface, enabling it to be serialized without the need for a "dummy" SerializableRunnable interface.

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