Custom serialization

What will the following code output?

import java.io.IOException;
import java.io.Serializable;

class CustomSerialization implements Serializable {
  
  private static final long serialVersionUID = -8385655899811016412L;
  
  private final int a;
  private final int b;
  
  public CustomSerialization() {
    a = 10;
    b = 20;
  }
  
  private void writeObject(java.io.ObjectOutputStream out) throws IOException {
    out.defaultWriteObject();
  }
  
  private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
  }
  
  @Override
  public String toString() {
    return Integer.toString(a) + " " + Integer.toString(b);
  }
  
  public static void main(String[] args) {
    CustomSerialization customSerialization = new CustomSerialization();
    // Function that serializes and deserializes object back and forth
    customSerialization = Utils.serializeDeserialize(customSerialization);
    System.out.println(customSerialization);
  }

}