If a serializable class contains a member (field) that is not serializable, attempting to serialize an instance of that class will result in a java.io.NotSerializableException being thrown at runtime. This happens because the serialization process includes serializing all fields of the class, including those of non-serializable types.

To fix this issue, you need to handle the non-serializable member in a way that allows proper serialization. Here are a few approaches you can take:

Make the Member Serializable:

The most straightforward solution is to make the non-serializable member serializable by implementing the Serializable interface for its class. This ensures that the member can be properly serialized along with the containing class.

Mark the Member as transient:

You can use the transient modifier to indicate that a specific member should not be serialized. When a member is marked as transient, it will be ignored during serialization and deserialization. You'll need to handle the initialization of the member separately upon deserialization. 

Custom Serialization (Optional):

If you need to perform custom serialization and deserialization for the non-serializable member, you can implement the writeObject and readObject methods in your serializable class. This allows you to define how the non-serializable member should be serialized and deserialized.