Java:来自 Set<String> 的枚举

2022-01-17 00:00:00 set collections enumeration java

我有一个简单的收藏问题.我有一个 Set 对象.我想要一个 <Set 中的 String 的 code>Enumeration.我需要一个 Enumeration<String>，因为我正在重写一个专门返回 Enumeration<String> 的方法.最干净/最好的方法是什么?

I have a simple collections question. I have a Set<String> object. I want an Enumeration<String> of the Strings in that Set. I need an Enumeration<String> since I am overriding a method that specifically returns an Enumeration<String>. What is the cleanest/best way to go about it?

推荐答案

无需编写自己的(尽管我将在下面留下实现以供后代使用) - 请参阅 Kevin Bourrillion 对 JDK 中的答案的回答.

There's no need to write your own (although I'll leave the implementation below for posterity) - see Kevin Bourrillion's answer for the one in the JDK.

如果你真的需要枚举，可以使用:

If you really need an enumeration, could could use:

Enumeration<String> x = new Vector(set).elements();

如果可能的话，最好使用 Iterable<E>...

It would be better to use Iterable<E> if at all possible though...

更好的选择是围绕 Iterator 编写一个小型包装类.这样你就不必为了找到 Enumeration<E> 的实现而复制一份:

A better alternative is to write a small wrapper class around Iterator<E>. That way you don't have to take a copy just to find an imlementation of Enumeration<E>:

import java.util.*;

class IteratorEnumeration<E> implements Enumeration<E>
{
    private final Iterator<E> iterator;

    public IteratorEnumeration(Iterator<E> iterator)
    {
        this.iterator = iterator;
    }

    public E nextElement() {
        return iterator.next();
    }

    public boolean hasMoreElements() {
        return iterator.hasNext();
    }

}


public class Test {
    public static void main(String[] args) {
        Set<String> set = new HashSet<String>(); 
        Enumeration<String> x = new IteratorEnumeration<String>(set.iterator());
    }
}

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