import java.net.InterfaceAddress;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;

public class InterfaceAddressNPE {

    public static void main(String[] args) {
        try {
            // Step 1: Get the hidden, parameter-less constructor of InterfaceAddress.
            // This is our secret entrance, as we can't use "new InterfaceAddress()".
            Constructor<InterfaceAddress> constructor = InterfaceAddress.class.getDeclaredConstructor();
            constructor.setAccessible(true); // Disable Java's access control checks.

            // Step 2: Create a "blank" instance of the object.
            // At this point, all its internal fields are uninitialized (i.e., null or 0).
            InterfaceAddress instance = constructor.newInstance();

            // Step 3: Get the private "address" field. This is the field that
            // the hashCode() method incorrectly assumes is never null.
            Field addressField = InterfaceAddress.class.getDeclaredField("address");
            addressField.setAccessible(true); // Again, disable access checks.

            // Step 4: The critical move. We explicitly set the "address" field to null.
            // We are creating a state that the class's public methods would never produce,
            // but which its hashCode() implementation fails to handle.
            addressField.set(instance, null);

            // Step 5: The moment of truth. Call hashCode() on our crafted object.
            // This is the landmine we are intentionally stepping on.
            instance.hashCode();

            // If we reach this line, it means no exception was thrown.
            // This would indicate the bug has been fixed in the JDK version being used.
            System.out.println("TEST FAILED: No NullPointerException was thrown. The bug might be fixed.");

        } catch (NullPointerException e) {
            // SUCCESS! The expected exception was caught.
            System.out.println("TEST PASSED: Successfully triggered the NullPointerException in hashCode().");
            System.out.println("This confirms the bug: a non-null object's hashCode() method must not throw an exception.");

        } catch (Exception e) {
            // This catches any other exceptions, like from the reflection setup.
            System.out.println("TEST FAILED: An unexpected exception occurred during setup.");
            e.printStackTrace();
        }
    }
}