Java Guava 或 Apache Commons Collections 中是否有 toArray() 的通用版本？
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Is there any generic version of toArray() in Guava or Apache Commons Collections?
提问by Mihai
What I'm looking for is a generic version of Object[] java.util.Collection.toArray()or a less verbose alternative to using T[] java.util.Collection.toArray(T[] array). I can currently write:
我正在寻找的是Object[] java.util.Collection.toArray()使用T[] java.util.Collection.toArray(T[] array). 我目前可以写：
Collection<String> strings;
String[] array = strings.toArray(new String[strings.size()]);
What I'm looking for is something like:
我正在寻找的是这样的：
@SuppressWarnings("unchecked")
public static <T> T[] toArray(Collection<T> collection, Class<T> clazz) {
return collection.toArray((T[]) Array.newInstance(clazz, collection.size()));
}
which I can then use as:
然后我可以将其用作：
String[] array = Util.toArray(strings, String.class);
So is anything like this implemented in Guava or in Commons Collections?
那么这样的东西是在 Guava 还是 Commons Collections 中实现的呢？
Of course I can write my own (the above), which seems to be as fast as toArray(T[] array).
当然我可以自己写（上面的），好像和toArray(T[] array)一样快。
采纳答案by axtavt
Iterables.toArray()from Guava.
Iterables.toArray()来自番石榴。
回答by assylias
You can shorten it with
你可以缩短它
String[] array = strings.toArray(new String[0]);
which also happens to be more efficient.
这也恰好更有效率。
With Java 8 you can also use this, but it seems unnecessarily complicated and is probably slower:
在 Java 8 中，您也可以使用它，但它似乎不必要地复杂并且可能更慢：
String[] array = strings.stream().toArray(String[]::new); // Java 8
