[英]Given a mutable class, how to make immutable a specific object of this class?
我得到了這個類,它對於我創建的每個實例顯然都是可變的,但我想知道是否有某種包裝器(或其他東西)來使這個類的一個特定對象不可變。 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;
}
@Override
public 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);
}
@Override
public 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;
}
}
我知道的唯一方法是實例化它並覆蓋能夠修改特定實例的方法:
Animal animal = new Animal("name", "commentary") {
@Override
public void setCommentary(String commentary) {
throw new UnsupportedOperationException("The Animal is immutable");
}
@Override
public void setName(String name) {
throw new UnsupportedOperationException("The Animal is immutable");
}
};
這也滿足了只有一個類的特定實例具有特殊行為的條件。
如果您需要更多它們,請創建一個充當裝飾器的包裝類(不完全是)。 不要忘記將類設置為final
否則您將能夠以我上面描述的方式覆蓋它的方法,並且它的不變性可能會中斷。
Animal animal = new ImmutableAnimal(new Animal("name", "commentary"));
final class ImmutableAnimal extends Animal {
public ImmutableAnimal(Animal animal) {
super(animal.getName(), animal.getCommentary());
}
@Override
public void setCommentary(String commentary) {
throw new UnsupportedOperationException("The Animal is immutable");
}
@Override
public void setName(String name) {
throw new UnsupportedOperationException("The Animal is immutable");
}
}
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