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  • list和数组转换

    2019-09-12 16:24:43
    1 数组转换List 调用Arrays类的静态方法asList。 asList public static <T> List<T> asList(T...a) Returns a fixed-size list backed by the ...

    1 数组转换为List

    调用Arrays类的静态方法asList。

    asList

    public static <T> List<T> asList(T... a)
    Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.) This method acts as bridge between array-based and collection-based APIs, in combination with  Collection.toArray(). The returned list is serializable and implements  RandomAccess.

    This method also provides a convenient way to create a fixed-size list initialized to contain several elements:

    List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");

    Parameters:
    a - the array by which the list will be backed
    Returns:
    a list view of the specified array

    用法:API中提供了一种使用的方法。更为常用的示例代码:

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

    2 List转换为数组

    这里的List以ArrayList为例,ArrayList的API提供了两种可供使用的函数。

    toArray

    public 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 sequence
    See Also:
    Arrays.asList(Object[])

    toArray

    public <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 list
    Throws:
    ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
    NullPointerException - if the specified array is null

    用法:示例代码:

    1. List<String> list = new ArrayList<String>();  
    2. list.add("str1");  
    3. list.add("str2");  
    4. int size = list.size();  
    5. String[] arr = (String[])list.toArray(new String[size]);//使用了第二种接口,返回值和参数均为结果  

    转载于:https://my.oschina.net/wswhr/blog/709863

    展开全文
  • List和数组转换

    2016-07-28 15:01:44
    主要以string为例,其他类型对应转换。 1. List转换成数 string[] str=list.ToArray(); 2. 数组[stringArray]转换List List list = new List(stringArray);

    主要以string为例,其他类型对应转换。

    1. List转换成数组

    string[] str=list.ToArray();

    2. 数组[stringArray]转换成List

    List<string> list = new List<string>(stringArray);

    展开全文
  • java List和数组转换

    2018-01-12 17:28:00
    集合转数 Collection提供了一个方法:toArray jdk1.5前:返回Object Object[] array = list.toArray();  返回String String[] array =list.toArray(new String[list.szie()]); 数组转集合 List<String>...

    集合转数组

    Collection提供了一个方法:toArray

    jdk1.5前:返回Object        Object[] array = list.toArray();

        返回String     String[] array =list.toArray(new String[list.szie()]);

    数组转集合

    List<String> list= Arrays.asList(array);

    不能扩容会抛出异常

     

    转载于:https://www.cnblogs.com/gjack/p/8276915.html

    展开全文
  • java list 和数组转换

    2016-09-15 14:21:13
    1 数组转换List 调用Arrays类的静态方法asList。 asList public static List asList(T... a) Returns a fixed-size list backed by the specified array. (Changes to the returned list "write ...

    点击打开链接

    1 数组转换为List

    调用Arrays类的静态方法asList。

    asList

    public static <T> List<T> asList(T... a)
    Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.) This method acts as bridge between array-based and collection-based APIs, in combination with Collection.toArray(). The returned list is serializable and implements RandomAccess.

    This method also provides a convenient way to create a fixed-size list initialized to contain several elements:

         List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");
     

    Parameters:
    a - the array by which the list will be backed
    Returns:
    a list view of the specified array

    用法:API中提供了一种使用的方法。更为常用的示例代码:

    [java] view plain copy
    1. String[] arr = new String[] {"str1""str2"};  
    2. List<String> list = Arrays.asList(arr);  

    2 List转换为数组

    这里的List以ArrayList为例,ArrayList的API提供了两种可供使用的函数。

    toArray

    public 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 sequence
    See Also:
    Arrays.asList(Object[])

    toArray

    public <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 list
    Throws:
    ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
    NullPointerException - if the specified array is null

    用法:示例代码:

    [java] view plain copy
    1. List<String> list = new ArrayList<String>();  
    2. list.add("str1");  
    3. list.add("str2");  
    4. int size = list.size();  
    5. String[] arr = (String[])list.toArray(new String[size]);//使用了第二种接口,返回值和参数均为结果  
    展开全文
  • 使用集合转数的方法,必须使用集合的 toArray(T[] array),传入的是类型完全一样的数组,大小就是 list.size()。 使用 toArray 带参方法,入参分配的数组空间不够大时,toArray 方法内部将重新分配内存空间,并...
  • 泛型数组(List为例)和 引用类型数组转换 基本类型数组转换 前置知识:泛型必须是引用类型,不能是基本类型 文章目录引用类型数组转换泛型数组 to 引用类型数组引用类型数组 to 泛型数组基本类型数组转换泛型数组 ...

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