创建单例数组的最佳方式

What is the "easiest" way for you to create a singleton (with exactly one element) Objects array in Java ?

在Java中创建单元素(只有一个元素)对象数组的“最简单”方法是什么?

6 个解决方案

#1

Object [] singleton = { new SomeObject() };

#2

The standard way is this:

标准的方法是:

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:

String[] arr = {"I am the one and only"};

Thanks aioobe, I keep forgetting this.

谢谢大家，我总是忘记这一点。

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，使事情更简单:

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)

(但是不能在编译时强制要求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，但是Stephen比我强。

#3

enum solution(anti reflect attack):

enum解决方案(抗反射攻击):

enum MySingleton{
    INSTANCE(new String[]{"a","b"});

    final String[] values;

    private MySingleton(String[] values) {
        this.values = values;
    }
}

reference it as:

参考它:

MySingleton.INSTANCE;

#4

This should do the job

这应该是可行的

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 Class object as an additional parameter.

该方法的通用版本使用起来有些笨拙，因为您需要将类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.

在SomeType[]{elem}表达式中嵌入更简单，这是我通常这样做的方法。

#5

You could do this:

你可以这样做:

String[] a = Collections.singletonList("SingleElement").toArray();

String[]= Collections.singletonList(“圈”).toArray();

Edit: Whoops! The above example doesn't compile. As stated in the comment, this can be done either as:

编辑:哎呀!上面的例子没有编译。如评论所述，可以这样做:

Object[] a = Collections.singletonList("SingleElement").toArray();
Or
String[] a = Collections.singletonList("SingleElement").toArray(new String[1]);

对象[]= Collections.singletonList(“圈”).toArray();或String[] a = collection . singletonlist(“singletonlist”)toArray(新的字符串[1]);

#6

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，它仍然比公认的答案更加冗长:

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化器语法时，它就变得非常方便。

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.

你可以自己想象其他的例子。

Also note, that the ArrayUtils.toArray() can wrap an arbitrary number of objects into array, not only a single one.

还要注意，ArrayUtils.toArray()可以将任意数量的对象包装到数组中，而不仅仅是单个对象。

#1

Object [] singleton = { new SomeObject() };

#2