英文:
Given a mutable class, how to make immutable a specific object of this class?
问题
我有这个类，显然对于我创建的每个实例都是可变的，但我想知道是否有一种包装器（或类似的东西）可以使得只有一个特定的这个类的对象是不可变的。例如 Collections.unmodifiableList(beanList)。
class Animal {private String name;private String commentary;public Animal(String nombre, String comentario) {this.name = nombre;this.commentary = comentario;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;Animal animal = (Animal) o;return Objects.equals(name, animal.name);}@Overridepublic int hashCode() {return Objects.hash(name);}public String getName() {return name;}public String getCommentary() {return commentary;}// 此处省略了setCommentary和setName方法，以及其他方法}
英文:
I got THIS class which is obviously mutable for every instance I create, but I want to know if there´s
some kind of wrapper (or something) to make just ONE specific object of THIS class immutable. e.g Collections.unmodifiableList(beanList).
class Animal {private String name;private String commentary;public Animal(String nombre, String comentario) {this.name = nombre;this.commentary = comentario;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;Animal animal = (Animal) o;return Objects.equals(name, animal.name);}@Overridepublic int hashCode() {return Objects.hash(name);}public String getName() {return name;}public String getCommentary() {return commentary;}public void setCommentary(String commentary) {this.commentary = commentary;}public void setName(String name) {this.name = name;}}
答案1
得分: 6
我所知道的唯一方法是实例化它并重写能够修改特定实例的方法：
Animal animal = new Animal("name", "commentary") {@Overridepublic void setCommentary(String commentary) {throw new UnsupportedOperationException("The Animal is immutable");}@Overridepublic void setName(String name) {throw new UnsupportedOperationException("The Animal is immutable");}};
这也满足了只有 类的一个特定实例 具有特殊行为的条件。
如果你需要更多类似的实例，可以创建一个充当装饰者（并非完全如此）的包装类。不要忘记 将这个类声明为 final，否则你可能会按照我上面描述的方式重写它的方法，从而破坏其不可变性。
Animal animal = new ImmutableAnimal(new Animal("name", "commentary"));
final class ImmutableAnimal extends Animal {public ImmutableAnimal(Animal animal) {super(animal.getName(), animal.getCommentary());}@Overridepublic void setCommentary(String commentary) {throw new UnsupportedOperationException("The Animal is immutable");}@Overridepublic void setName(String name) {throw new UnsupportedOperationException("The Animal is immutable");}}
英文:
The only way I am aware of is to instantiate it and override the methods that are able to modify the particular instance:
Animal animal = new Animal("name", "commentary") {@Overridepublic void setCommentary(String commentary) {throw new UnsupportedOperationException("The Animal is immutable");}@Overridepublic void setName(String name) {throw new UnsupportedOperationException("The Animal is immutable");}};
This also satisfied the condition that only one specific instance of the class has a special behavior.
If you need more of them, create a wrapping class that acts as a decorator (isn't exactly). Do not forget to make the class as final otherwise you would be able to override its method in the way I described above and its immutability might break.
Animal animal = new ImmutableAnimal(new Animal("name", "commentary"));
final class ImmutableAnimal extends Animal {public ImmutableAnimal(Animal animal) {super(animal.getName(), animal.getCommentary());}@Overridepublic void setCommentary(String commentary) {throw new UnsupportedOperationException("The Animal is immutable");}@Overridepublic void setName(String name) {throw new UnsupportedOperationException("The Animal is immutable");}}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论