How to serialize an object of your class if one of its fields is not serializable?

Use the @Transient annotation (if the field does not need to be saved) or provide custom serialization/deserialization logic using @JsonAdapter, writeReplace/readResolve, or a custom TypeAdapter (for example, in Gson).

Example with @Transient in Kotlin (for Serializable):

import java.io.Serializable

data class User(
    val id: Int,
    @Transient val nonSerializableField: Any // Field will not be serialized
) : Serializable

Example with @JsonAdapter in Gson:

import com.google.gson.annotations.JsonAdapter;

class MyClass {
    int id;
    @JsonAdapter(NonSerializableFieldAdapter.class)
    NonSerializableField nonSerializableField; // Field will be serialized using the adapter
}