Java 创建单例数组的最佳方法
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Best way to create singleton array
提问by Manuel Selva
What is the "easiest" way for you to create a singleton (with exactly one element) Objects array in Java ?
在 Java 中创建单例（只有一个元素）对象数组的“最简单”方法是什么？
采纳答案by KristofMols
Object [] singleton = { new SomeObject() };
回答by Sean Patrick Floyd
The standard way is this:
标准方法是这样的：
String[] arr = new String[]{"I am the one and only"};
I'm afraid it doesn't get much simpler than this.
恐怕没有比这更简单的了。
Edit: it does:
编辑：它确实：
String[] arr = {"I am the one and only"};
Thanks aioobe, I keep forgetting this.
谢谢aioobe，我一直忘记这个。
Of course if you often create array you can create a helper method that makes things a bit simpler:
当然，如果你经常创建数组，你可以创建一个帮助方法，让事情变得更简单：
public static <T> T[] asArray(T... items){
return items;
}
String[] arr = asArray("I am the one and only");
(But you can't enforce at compile time that it will be an array with only one element)
（但你不能在编译时强制它是一个只有一个元素的数组）
Next I was going to write a singleton array method, but Stephen beat me to that.
接下来我要写一个单例数组方法，但斯蒂芬打败了我。
回答by Stephen C
This should do the job
这应该可以完成工作
public SomeType[] makeSingletonArray(SomeType elem) {
return new SomeType[]{elem};
}
A generic version of this method would be somewhat awkward to use, since you would need to pass it a Classobject as an additional parameter.
此方法的通用版本使用起来有些尴尬，因为您需要将一个Class对象作为附加参数传递给它。
Inlining the SomeType[]{elem}expression is simpler, and that's how I'd normally do this.
内联SomeType[]{elem}表达式更简单，这就是我通常这样做的方式。
回答by Nate W.
You could do this:
你可以这样做：
String[] a = Collections.singletonList("SingleElement").toArray();
String[] a = Collections.singletonList("SingleElement").toArray();
Edit:Whoops! The above example doesn't compile. As stated in the comment, this can be done either as:
编辑：哎呀！上面的例子不能编译。正如评论中所述，这可以通过以下方式完成：
Object[] a = Collections.singletonList("SingleElement").toArray();
OrString[] a = Collections.singletonList("SingleElement").toArray(new String[1]);
Object[] a = Collections.singletonList("SingleElement").toArray();
或者String[] a = Collections.singletonList("SingleElement").toArray(new String[1]);
回答by u290629
enum solution(anti reflect attack):
枚举解决方案（反反射攻击）：
enum MySingleton{
INSTANCE(new String[]{"a","b"});
final String[] values;
private MySingleton(String[] values) {
this.values = values;
}
}
reference it as:
将其引用为：
MySingleton.INSTANCE;
回答by Yoory N.
If your project is already using Apache Commons lib, you can stick to ArrayUtils.toArray()method.
如果您的项目已经在使用 Apache Commons lib，您可以坚持使用ArrayUtils.toArray()方法。
String[] arr = ArrayUtils.toArray("The string");
// or if using static import
String[] arr = toArray("The string");
Even if using static import it is still more verbose than the accepted answer:
即使使用静态导入，它仍然比接受的答案更冗长：
String[] arr = {"The string"};
But it comes very handy when compact array initializer syntax is not allowed.
但是当不允许使用紧凑数组初始值设定项语法时，它会非常方便。
Some examples:
一些例子：
someMethod(toArray("The string"), /* other params */);
return toArray("The string");
@DataProvider
public Object[][] someDataProvider() {
return rangeClosed(-12, +12)
.map(HOURS::toMillis).boxed()
.map(ArrayUtils::toArray)
.toArray(Object[][]::new);
}
You can imagine any other examples yourself.
您可以自己想象任何其他示例。
Also note, that the ArrayUtils.toArray()can wrap an arbitrary number of objects into array, not only a single one.
另请注意，ArrayUtils.toArray()可以将任意数量的对象包装到数组中，而不仅仅是一个。
