Difference between Serialization and Externalization in Java

Serialization and externalization both are the processes of converting an object to stream byte and storing byte stream in database or memory. The class which implements java.io.Serializable interface can be serialized. On the other hand, externalization used for custom serialization based on the requirement in the application. Externalization extends java.io.Serializable. 

Example of Externalizable

class ExternalizableExample implements Externalizable {
   Integer id;
   @Override
   public void writeExternal(ObjectOutput out) throws IOException {
      out.writeInt( id );
   }
   @Override
   public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
      this.id = in.readInt();
   }
}

Example of Serializable

class SerializableExample implements Serializable {
   private static final long serialVersionUID = 5081877L;
   String name;
}