java - 接口方法中的返回类型应该是什么

Question

我有两节课。Status1和Status2

这两种状态有一个共同点：

protected A a;

和一个不常见的：

class Status1 {
    protected A a;
    protected ListStatus1.B version;
}

B在课堂static class内Status1

class Status2 {
    protected A a;
    protected Status2.C version;
}

C在课堂static class内Status2

所以现在我想创建界面Status

在这里我可以补充variable A。现在我需要添加getVersion应该返回静态类的方法Status1 / Status2

protected abstract ?? getVersion();

但我不知道return type应该有什么

我尝试添加到这个接口静态类和这个类返回但没有成功

Answer 1

“正确的做法”是让两个静态类 B 和 C 实现一个共同的 empty interface，我们称之为“版本化”

public interface Versioned{}

static class B implements Versioned{
...
}
static class C implements Versioned{
...
}

之后，您可以编写：

 protected abstract Versioned getVersion();

并且您的方法将被允许返回 B 或 C。

Answer 2

I think Object should do the trick!

however, while accessing any fields of the object you might face problems. Thus, I suggest you to have an interface Version which is implemented by the inner classes of both the statuses.

Hope this helps,

Cheers

Answer 3

If the difference between Status1.B and Status2.C is essential for your object model, you can make Status generic:

public interface Status<V> {
    public V getVersion();
}

public class Status1 implements Status<Status1.B> {
    public Status1.B getVersion() { ... }
    ...
}

Otherwise you can introduce an interface for both version classes, as suggested by other answers.

Answer 4

One way is to create an interface (let's call it IVersion) and make both version classes implement that interface. The getVersion() method can then return this interface:

protected abstract IVersion getVersion();