Java 将 ArrayList 转换为对象数组
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Convert an ArrayList to an object array
提问by marionmaiden
Is there a command in java for conversion of an ArrayList into a object array. I know how to do this copying each object from the arrayList into the object array, but I was wondering if would it be done automatically.
java中是否有将ArrayList转换为对象数组的命令。我知道如何将每个对象从 arrayList 复制到对象数组中，但我想知道它是否会自动完成。
I want something like this:
我想要这样的东西：
ArrayList<TypeA> a;
// Let's imagine "a" was filled with TypeA objects
TypeA[] array = MagicalCommand(a);
采纳答案by Mark Elliot
Something like the standard Collection.toArray(T[])should do what you need (note that ArrayListimplements Collection):
像标准Collection.toArray(T[])应该做你需要的东西（注意ArrayList实现Collection）：
TypeA[] array = a.toArray(new TypeA[a.size()]);
On a side note, you should consider defining ato be of type List<TypeA>rather than ArrayList<TypeA>, this avoid some implementation specific definition that may not really be applicable for your application.
附带说明一下，您应该考虑定义a为 typeList<TypeA>而不是ArrayList<TypeA>，这可以避免某些可能并不真正适用于您的应用程序的特定于实现的定义。
Also, please see this questionabout the use of a.size()instead of 0as the size of the array passed to a.toArray(TypeA[])
另外，请参阅该问题有关的使用a.size()，而不是0作为数组传递给大小a.toArray(TypeA[])
回答by Rachel
Yes. ArrayListhas a toArray()method.
是的。ArrayList有toArray()方法。
http://java.sun.com/javase/6/docs/api/java/util/ArrayList.html
http://java.sun.com/javase/6/docs/api/java/util/ArrayList.html
回答by jweber
TypeA[] array = (TypeA[]) a.toArray();
回答by Shashank T
You can use this code
您可以使用此代码
ArrayList<TypeA> a = new ArrayList<TypeA>();
Object[] o = a.toArray();
Then if you want that to get that object back into TypeA just check it with instanceOf method.
然后，如果您希望将该对象返回到 TypeA，只需使用 instanceOf 方法检查它。
回答by user527619
Convert an ArrayList to an object array
将 ArrayList 转换为对象数组
ArrayList has a constructor that takes a Collection, so the common idiom is:
ArrayList 有一个接受 Collection 的构造函数，所以常见的习惯用法是：
List<T> list = new ArrayList<T>(Arrays.asList(array));
Which constructs a copy of the list created by the array.
它构造了由数组创建的列表的副本。
now, Arrays.asList(array)will wrap the array, so changes to the list
will affect the array, and visa versa. Although you can't add or remove
现在，Arrays.asList(array)将包装数组，因此对列表的更改将影响数组，反之亦然。虽然你不能添加或删除
