我如何正確覆蓋在java中的繼承等於？

Question

我使用hibernate和id ...用於持久性（這就是爲什麼它在比較中被省略）。 （另外，使用谷歌番石榴幫手等於）

HolidayPackageVariant：

public abstract class HolidayPackageVariant { 
    private Integer idHolidayPackageVariant; 
    private HolidayPackage holidayPackage; 
    private String typeHolidayPackage; 

@Override 
public boolean equals(Object obj) { 
    if (obj == this) 
     return true; 
    if(obj == null) 
     return false; 

    if (getClass().equals(obj.getClass())) { 
     final HolidayPackageVariant otherPackageVariant = (HolidayPackageVariant) obj; 
     return Objects.equal(getTypeHolidayPackage(),otherPackageVariant.getTypeHolidayPackage()) 
       && Objects.equal(getHolidayPackage(), 
         otherPackageVariant.getHolidayPackage()); 
    } 
    return false; 
} 

@Override 
public int hashCode() { 
    return Objects.hashCode(getTypeHolidayPackage(), getHolidayPackage()); 
} 

FlightHolidayPackageVariant：

public final class FlightHolidayPackageVariant extends HolidayPackageVariant{ 
    private Destination originCity; 
    public boolean equals(Object obj) { 
    // .. 

我應該完全覆蓋了equals（）或者我應該調用super.equals（.. 。） 某種程度上來說 ？

Answer 1

繼Secret of Equals：

HolidayPackageVariant：

public abstract class HolidayPackageVariant { 
    private Integer idHolidayPackageVariant; 
    private HolidayPackage holidayPackage; 
    private String typeHolidayPackage; 

    @Override 
    public boolean equals(Object obj) { 
     if (obj == this) return true; 
     if(obj == null) return false; 

     if (getClass().equals(obj.getClass())) { 
      final HolidayPackageVariant otherPackageVariant = (HolidayPackageVariant) obj; 
      return Objects.equal(getTypeHolidayPackage(),otherPackageVariant.getTypeHolidayPackage()) 
        && Objects.equal(getHolidayPackage(), 
          otherPackageVariant.getHolidayPackage()); 
     } 
     return false; 
    } 
} 

---

FlightHolidayPackageVariant：

public final class FlightHolidayPackageVariant extends HolidayPackageVariant{ 
    private Destination originCity; 

    @Override 
    public boolean equals(Object obj) { 

     if(super.equals(obj)){ 
      return Objects.equal(getOriginCity(), 
        ((FlightHolidayPackageVariant)(obj)).getOriginCity()); 
     } 
     return false; 
    } 
} 

這將確保變種只有相同類型是彼此相等。

Answer 2

這就是你應該如何實現數據對象：不允許繼承，僅限構成。

這些是不可變的對象，但您可能想要修改它們，因此在需要時刪除final。你也可以從類定義中刪除final，因爲Hibernate不支持它，但在這種情況下，你應該記錄這些類不適合繼承。

主要的優點是有效的Java加上描述的所有的，在這種情況下，你不必通過Hibernate管理繼承，這有時會是一個真正的痛苦。

public final class HolidayPackageVariant { 
    private final Integer idHolidayPackageVariant; 
    private final HolidayPackage holidayPackage; 
    private final String typeHolidayPackage; 

    ... 

    @Override 
    public boolean equals(Object obj) { 
    if (obj == this) 
     return true; 
    if (!(obj instanceof HolidayPackageVariant)) 
     return false; 

    HolidayPackageVariant that = (HolidayPackageVariant) obj; 
    return Objects.equal(this.typeHolidayPackage, that.typeHolidayPackage) 
     && Objects.equal(this.holidayPackage, that.holidayPackage); 
    } 

    @Override 
    public int hashCode() { 
    return Objects.hashCode(this.typeHolidayPackage, this.holidayPackage); 
    } 
} 

public final class FlightHolidayPackageVariant { 
    private HolidayPackageVariant holidayPackageVariant; 
    private Destination originCity; 

    ... 

    public HolidayPackageVariant asHolidayPackageVariant() { 
    return this.holidayPackageVariant; 
    } 

    public boolean equals(Object obj) { 
    if (obj == this) 
     return true; 
    if (!(obj instanceof FlightHolidayPackageVariant)) 
     return false; 

    FlightHolidayPackageVariant that = (FlightHolidayPackageVariant) obj; 
    return Objects.equal(this.holidayPackageVariant, that.holidayPackageVariant) 
     && Objects.equal(this.originCity, that.originCity); 
    } 

    @Override 
    public int hashCode() { 
    return Objects.hashCode(this.holidayPackageVariant, this.originCity); 
    } 
}