ClassCastException字符串到MValue, java 8 [duplicate]

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ClassCast error: Java 7 vs Java 8 1 answer
ClassCast错误:Java 7 vs Java 8 1答案

I have an interface

我有一个接口

public interface MValue extends SomeOtherInterface, Serializable

and I use it in another interface like so

我把它用在另一个界面上

    public interface DomainObject extends Iterable<FieldValueAssociation>, Cloneable, Serializable {
     void add(DomainField field, MValue... values);
<T> T get(DomainField field);
    }

and when I call this in some other class I set

当我在其他类中调用这个时。

subDomain.add(DomainField.ZIP, d.get(DomainField.ZIP));

On java 7 this works fine, but on java 8 I get java.lang.ClassCastException: java.lang.String cannot be cast to net.blabla.domain.MValue

在java 7上，这很好，但是在java 8上我得到了java.lang。ClassCastException:. lang。不能将字符串转换为net.blabla.domain.MValue。

d.get(DomainField.ZIP) should return String, and it is, but it cannot be casted to MValue, and I dont know why? Can someone explain or refer me to some documentation. Thanks.

get(DomainField.ZIP)应该返回字符串，它是，但是它不能被转换为MValue，我不知道为什么?有人能给我解释或推荐一些文件吗?谢谢。

1 个解决方案

#1

So does that work?

所以这工作吗?

subDomain.add(DomainField.ZIP, d.<String>get(DomainField.ZIP));

Here I explicitly give the type for T as being String, type checking will happen nevertheless, but it makes clear to the compiler what is expected. This call should work for Java 7 and 8.

在这里，我明确地将T的类型指定为字符串，但是类型检查仍然会发生，但是它清楚地告诉编译器什么是期望的。这个调用应该适用于Java 7和8。

#1