Java List與數組之間的轉換

標籤：point   轉換   rmi   return   數組   ted   inter   lis   樣本   

1、數組轉List

String[] arr = new String[] {"str1", "str2"};  List<String> list = Arrays.asList(arr);  

2、List轉數組

這裡的List以ArrayList為例，ArrayList的API提供了兩種可供使用的函數。

第一種：

toArraypublic Object[] toArray()Returns an array containing all of the elements in this list in proper sequence (from first to last element).The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.This method acts as bridge between array-based and collection-based APIs.Specified by:toArray in interface Collection<E>Specified by:toArray in interface List<E>Overrides:toArray in class AbstractCollection<E>Returns:an array containing all of the elements in this list in proper sequenceSee Also:Arrays.asList(Object[])

　　第二種：

toArraypublic <T> T[] toArray(T[] a)Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)Specified by:toArray in interface Collection<E>Specified by:toArray in interface List<E>Overrides:toArray in class AbstractCollection<E>Parameters:a - the array into which the elements of the list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.Returns:an array containing the elements of the listThrows:ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this listNullPointerException - if the specified array is null

　　樣本：

List<String> list = new ArrayList<String>();  list.add("str1");  list.add("str2");  int size = list.size();  String[] arr = (String[])list.toArray(new String[size]);//使用了第二種介面，傳回值和參數均為結果  

　　

Java List與數組之間的轉換