编码技巧 - 交集类型和 Java 枚举

Question

Closed. This question needs details or clarity. It is not currently accepting answers.

---

想要改进这个问题？通过编辑这篇文章添加详细信息并澄清问题。

11 年前已关闭。

Answer 1

您可以只使用 Commons Enum 实现：

http://commons.apache.org/lang/api-2.3/org/apache/commons/lang/enums/Enum.html

它允许您创建可以子类化的枚举。

Answer 2

这更简单，它能满足您的要求吗？

import java.util.*;
interface Tree{
    Tree parent();
    Set<Tree> children();
}
enum PrimaryColor implements Tree {
    Red,Green,Blue;
    @Override public Tree parent() {
        return null;
    }
    @Override public Set<Tree> children() {
        return Collections.unmodifiableSet(children);
    }
    final Set<Tree> children=new LinkedHashSet<Tree>();
}
enum PastelColor implements Tree {
    Pink(PrimaryColor.Red),HotPink(PrimaryColor.Red),Rockmelon(PrimaryColor.Green),SkyBlue(PrimaryColor.Blue),BabyBlue(PrimaryColor.Blue);
    PastelColor(final PrimaryColor primaryColor) {
        this.primaryColor=primaryColor;
        if (primaryColor!=null) primaryColor.children.add(this);
    }
    @Override public Tree parent() {
        return primaryColor;
    }
    @Override public Set<Tree> children() {
        return Collections.emptySet();
    }
    double percent() {
        return primaryColor.children().size()*100./EnumSet.allOf(super.getClass()).size();
    }
    private final PrimaryColor primaryColor;
}
public class Main{
    static double percent(final Tree tree) {
        final Tree parent=tree.parent();
        if (tree instanceof Enum) { return parent.children().size()*100./((Enum)tree).getClass().getEnumConstants().length; }
        else throw new RuntimeException("strange tree!");
    }
    public static void main(String[] args) {
        System.out.println("one way");
        for(PastelColor pastelColor:PastelColor.values())
            System.out.println(pastelColor+" "+pastelColor.percent());
        System.out.println("another way");
        for(PastelColor pastelColor:PastelColor.values())
            System.out.println(pastelColor+" "+percent(pastelColor));
    }
}