java - 如何实现将返回枚举的具体类型的方法签名？

Question

我想创建一个方法，该方法将从枚举中返回四种类型之一。因此，如果有人想要 SCAN_RANK_GROUPS 过滤器，我如何才能使方法的返回类型成为 Rank，或者如果有人想要 SCAN_MEMBERS 它将返回成员。我该怎么做呢？

public <T> T scanTemporaryStorage(ScanFilters filter) {
    return (T) filter.performOperation();
}

public enum ScanFilters {

    SCAN_RANK_GROUPS {
                @Override
                public <Rank> Rank performOperation() {
                }
            },
    SCAN_MEMBERS {

                @Override
                public <Member> Member performOperation() {
                }

            };

    public abstract <T> T performOperation();

}

Answer 1

这是不可能的。我的建议是为 Rank 和 Member 创建一个父类(super class) Scannable，并使用它:

public Scannable scanTemporaryStorage(ScanFilters filter) {
    return filter.performOperation();
}

public enum ScanFilters {

    SCAN_RANK_GROUPS {
                @Override
                public Scannable performOperation() {
                }
            },
    SCAN_MEMBERS {

                @Override
                public Scannable performOperation() {
                }
            };

    public abstract Scannable performOperation();

}

父类 Scannable 将拥有所有共享方法:

public abstract class Scannable {

    // have all the methods in Rank and Member
}

并让您的类(class)对其进行扩展。

public class Rank extends Scannable

public class Member extends Scannable