Here is an example of how to use the SerializedString class from the Apache Commons IO library:

import org.apache.commons.io.output.SerializedString;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class Example {
    public static void main(String[] args) throws IOException {
        // Create a serializable object
        Serializable obj = "Hello World";

        // Create a ByteArrayOutputStream
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        // Create an ObjectOutputStream
        ObjectOutputStream out = new ObjectOutputStream(baos);

        // Serialize the object
        out.writeObject(obj);
        out.flush();
        out.close();

        // Create a SerializedString
        SerializedString serialized = new SerializedString(baos.toByteArray());

        // Get the original object
        Serializable original = serialized.getOriginal();

        // Print the original object
        System.out.println(original);
    }
}

In this example, the SerializedString class is being used to serialize an object to a byte array and then deserialize it back to the original object. A Serializable object is created, then it's serialized using the ObjectOutputStream and ByteArrayOutputStream classes. The SerializedString class is then used to create an object which holds the serialized object in a byte array. The getOriginal() method is used to retrieve the original object.

The SerializedString class is useful when you want to serialize an object to a byte array and then deserialize it back to the original object. This can be useful for example when you want to cache an object in the memory and want to deserialize it later.

It's worth noting that the SerializedString class is based on the Java's built-in serialization mechanism, so it's important to be familiar with the basics of Java serialization and the issues that arise from it.