如何将arrayList的元素传递给可变参数函数 [英] How to pass elements of an arrayList to variadic function

问题描述

我有一个充满元素的 arrayList.我想将该数组列表的元素作为参数传递给可变参数函数.

I've got an arrayList filled with elements. I would like to pass the elements of that array list as arguments to a variadic function.

我的功能

public SequenceEntityModifier(final IEntityModifier... pEntityModifiers)

我的数组列表

ArrayList<IEntityModifier> arr = new ArrayList<IEntityModifier>();
arr.add(new MoveXModifier(1, 50, 120));
arr.add(new MoveXModifier(1, 120, 50));

我想将它传递给函数，就像我会单独传递它们一样.

I'd like to pass it to the function as if I would pass them individually.

new SequenceEntityModifier( /* elements of arr here */ );

这样的事情可能吗?

提前致谢.

推荐答案

只需:

new SequenceEntityModifier(arr.toArray(new IEntityModifier[arr.size()]));

这会将 ArrayList 复制到给定的数组并返回它.所有可变参数函数也可以为参数采用数组，因此:

This copies the ArrayList to the given array and returns it. All vararg functions can also take arrays for the argument, so for:

public void doSomething(Object... objs)

所有合法的电话是:

doSomething(); // Empty array
doSomething(obj1); // One element
doSomething(obj1, obj2); // Two elements
doSomething(new Object[] { obj1, obj2 }); // Two elements, but passed as array

一个警告:

涉及原始数组的 Vararg 调用不能像您期望的那样工作.例如:

Vararg calls involving primitive arrays don't work as you would expect. For example:

public static void doSomething(Object... objs) {
    for (Object obj : objs) {
        System.out.println(obj);
    }
}

public static void main(String[] args) {
    int[] intArray = {1, 2, 3};
    doSomething(intArray);
}

人们可能希望这会在单独的行上打印 1、2 和 3.相反，它会打印类似 [I@1242719c(int[] 的默认 toString 结果)之类的内容.这是因为它最终会创建一个带有一个元素的 Object[]，即我们的 int[]，例如:

One might expect this to print 1, 2, and 3, on separate lines. Instead, it prints something like [I@1242719c (the default toString result for an int[]). This is because it's ultimately creating an Object[] with one element, which is our int[], e.g.:

// Basically what the code above was doing
Object[] objs = new Object[] { intArray };

同样适用于 double[]、char[] 和其他原始数组类型.请注意，这可以通过将 intArray 的类型更改为 Integer[] 来解决.如果您使用现有数组，这可能并不简单，因为您无法将 int[] 直接转换为 Integer[](请参阅 这个问题，我特别喜欢ArrayUtils.toObject 来自 Apache Commons Lang).

Same goes for double[], char[], and other primitive array types. Note that this can be fixed simply by changing the type of intArray to Integer[]. This may not be simple if you're working with an existing array since you cannot cast an int[] directly to an Integer[] (see this question, I'm particularly fond of the ArrayUtils.toObject methods from Apache Commons Lang).

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