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

问题描述

我有一个arrayList元素。我想将数组列表的元素作为变量函数的参数传递。

我的函数

  public SequenceEntityModifier（final IEntityModifier ... pEntityModifiers）
  

<

  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，就像我们单独传递它们一样。

  new SequenceEntityModifier（/ * arr here * /）元素; 
  

这样的东西可能吗？

提前感谢。

解决方案

>

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

这会将 ArrayList 复制到给定数组并返回它。所有vararg函数也可以为参数取数组，因此：

  public void doSomething（Object ... objs）
  

所有合法来电皆为：

  doSomething（）; //空数组
 doSomething（obj1）; //一个元素
 doSomething（obj1，obj2）; //两个元素
 doSomething（new Object [] {obj1，obj2}）; //两个元素，但作为数组传递
  

一个警告： p>

涉及原始数组的Vararg调用不会按预期工作。例如：

  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} $ b $ d doSomething（intArray）; 
} 
  

可能希望这可以打印 1 ， 2 和 3 相反，它会打印 [I @ 1242719c （默认 toString result for a int [] ）。这是因为它最终用一个元素创建一个 Object [] ，这是我们的 int [] ，例如： / p>

  //基本上上面的代码执行的操作
 Object [] objs = new Object [] {intArray}; 
   
 
 
  double []  code> char [] 和其他原始数组类型。注意，这可以简单地通过将 intArray 的类型更改为 Integer [] 来修复。如果你使用现有的数组，这可能不简单，因为你不能直接把 int [] 转换为 Integer [] （请参阅此问题，我特别喜欢ArrayUtils.toObject 方法，来自 Apache Commons Lang ）。
 
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.

My function 
public SequenceEntityModifier(final IEntityModifier... pEntityModifiers)
My ArrayList
ArrayList<IEntityModifier> arr = new ArrayList<IEntityModifier>();
arr.add(new MoveXModifier(1, 50, 120));
arr.add(new MoveXModifier(1, 120, 50));
I'd like to pass it to the function as if I would pass them individually. 
new SequenceEntityModifier( /* elements of arr here */ );
Is something like this possible? 

Thanks in advance.
解决方案
Just do:
new SequenceEntityModifier(arr.toArray(new IEntityModifier[arr.size()]));
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)
All the legal calls are:
doSomething(); // Empty array
doSomething(obj1); // One element
doSomething(obj1, obj2); // Two elements
doSomething(new Object[] { obj1, obj2 }); // Two elements, but passed as array
One caveat:

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);
}
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 };
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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