何时使用Getter和Setter进行辩护

public class Fridge {
  private List objects;
  private Date warranty;

  /** How the warranty is stored internally is a detail. */
  public Fridge( Date warranty ) {
    // The Fridge can set its internal warranty, but it is not re-exposed.
    setWarranty( warranty );
  }

  /** Doesn't expose how the fridge knows it is empty. */
  public boolean isEmpty() {
    return getObjects().isEmpty();
  }

  /** When the fridge has no more room... */
  public boolean isFull() {
  }

  /** Answers whether the given object will fit. */
  public boolean canStore( Object o ) {
    boolean result = false;

    // Clients may not ask how much room remains in the fridge.
    if( o instanceof PhysicalObject ) {
      PhysicalObject po = (PhysicalObject)o;

      // How the fridge determines its remaining usable volume is a detail.
      // How a physical object determines whether it fits within a specified
      // volume is also a detail.
      result = po.isEnclosedBy( getUsableVolume() );
    }

     return result;
  }

  /** Doesn't expose how the fridge knows its warranty has expired. */
  public boolean isPastWarranty() {
    return getWarranty().before( new Date() );
  }

  /** Doesn't expose how objects are stored in the fridge. */
  public synchronized void store( Object o ) {
    validateExpiration( o );

    // Can the object fit?
    if( canStore( o ) ) {
      getObjects().add( o );
    }
    else {
      throw FridgeFullException( o );
    }
  }

  /** Doesn't expose how objects are removed from the fridge. */
  public synchronized void remove( Object o ) {
    if( !getObjects().contains( o ) ) {
      throw new ObjectNotFoundException( o );
    }

    getObjects().remove( o );

    validateExpiration( o );
  }

  /** Lazily initialized list, an implementation detail. */
  private synchronized List getObjects() {
    if( this.list == null ) { this.list = new List(); }
    return this.list;
  }

  /** How object expiration is determined is also a detail. */
  private void validateExpiration( Object o ) {
    // Objects can answer whether they have gone past a given
    // expiration date. How each object "knows" it has expired
    // is a detail. The Fridge might use a scanner and
    // items might have embedded RFID chips. It's a detail hidden
    // by proper encapsulation.
    if( o implements Expires && ((Expires)o).expiresBefore( today ) ) {
      throw new ExpiredObjectException( o );
    }
  }

  /** This creates a copy of the warranty for immutability purposes. */
  private void setWarranty( Date warranty ) {
    assert warranty != null;
    this.warranty = new Date( warranty.getTime() )
  }
}

connection.setUser("dukie");
connection.setPwd("duke");
connection.initialize();

connection.connect("dukie","duke");

myObject.GetStatus();
myObject.SomeCapabilitySwitch = true;

class Fridge
  attr_accessor :cheese
end

def go_shopping fridge
  fridge.cheese += 5
end

class Fridge
  attr_accessor :cheese

  def cheese
    @cheese || 0
  end
end