Arrays.asList()返回只读的List

我就是我 2022-08-19 13:13 80阅读 0赞

**List<Integer> list = Arrays.asList(1, 2, 3);**

**list.clear(); // throws java.lang.UnsupportedOperationException**

**对Arrays.asList()转化的List是一个固定长度的List，不支持add() remove() clear()等操作**

**Arrays.asList()返回的是一个ArrayList对象**

@SafeVarargs  
@SuppressWarnings( "varargs")  
**public**  **static** <T> List<T> asList(T... a) \{  
    **return**  **new** ArrayList<>(a);  
\}

而这个类继承自AbstractList类

**在AbstractList中而这个类中实现的所有对list的数据编辑操作都会抛出UnsupportedOperationException异常**

*/\*\**  
*    \* \{@inheritDoc\}*  
*    \**  
*    \* <p>This implementation always throws an*  
*    \* \{@code UnsupportedOperationException\}.*  
*    \**  
*    \* @throws UnsupportedOperationException \{@inheritDoc\}*  
*    \* @throws ClassCastException            \{@inheritDoc\}*  
*    \* @throws NullPointerException          \{@inheritDoc\}*  
*    \* @throws IllegalArgumentException      \{@inheritDoc\}*  
*    \* @throws IndexOutOfBoundsException     \{@inheritDoc\}*  
*    \*/*  
    **public** E set( **int** index, E element) \{  
        **throw**  **new** UnsupportedOperationException();  
   \}  
  
     */\*\**  
*    \* \{@inheritDoc\}*  
*    \**  
*    \* <p>This implementation always throws an*  
*    \* \{@code UnsupportedOperationException\}.*  
*    \**  
*    \* @throws UnsupportedOperationException \{@inheritDoc\}*  
*    \* @throws ClassCastException            \{@inheritDoc\}*  
*    \* @throws NullPointerException          \{@inheritDoc\}*  
*    \* @throws IllegalArgumentException      \{@inheritDoc\}*  
*    \* @throws IndexOutOfBoundsException     \{@inheritDoc\}*  
*    \*/*  
    **public**  **void** add( **int** index, E element) \{  
        **throw**  **new** UnsupportedOperationException();  
   \}  
  
*/\*\**  
*    \* \{@inheritDoc\}*  
*    \**  
*    \* <p>This implementation always throws an*  
*    \* \{@code UnsupportedOperationException\}.*  
*    \**  
*    \* @throws UnsupportedOperationException \{@inheritDoc\}*  
*    \* @throws IndexOutOfBoundsException     \{@inheritDoc\}*  
*    \*/*  
    **public** E remove( **int** index) \{  
        **throw**  **new** UnsupportedOperationException();  
   \}

**所以Arrays.asList()返回的list是只读的并不能对list的数据进行相关修改！**