Here is an example of how to use the logback.core.spi.HardenedObjectInputStream class to deserialize an object from a file:

import java.io.FileInputStream;
import java.io.IOException;
import logback.core.spi.HardenedObjectInputStream;

public class Main {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("objects.bin");
            HardenedObjectInputStream in = new HardenedObjectInputStream(fis);

            Object obj = in.readObject();
            System.out.println("Object: " + obj);

            in.close();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

In this example, an instance of HardenedObjectInputStream is created and configured to read from a file called "objects.bin" which should have serialized objects.

The readObject() method is used to read an Object from the input stream, it also performs a number of security checks before accepting the deserialized object.

It's important to close the HardenedObjectInputStream after use to release the resources it holds.

The HardenedObjectInputStream is intended to be used as a replacement for ObjectInputStream and it provides an improved security by hardening the deserialization process with additional checks on the deserialized data.