@Entity public class AnEntity {

    // With field based access fields are persistent by default
    private int someField;
    private String someOtherField;

    // Relationships among entities must be annotated
    @OneToMany private Collection <AnotherEntity> relatedEntities;

    // Every entity must have a primary key
    @Id private long aKeyField;

    // Field that is not persistent
    @Transient private String aTransientString;

    // Version field for optimistic concurrency
    @Version private long version = 0L;

    // Obligatory constructor with no arguments
    public AnEntity () { ... }

    // Additional business methods ...
    public void myMethodOne (int iArgument) { ... }
    public int myMethodTwo (Object oArgument) { ... }
}