asList(T... a)返回的是一个固定大小的list集合
源码分析：
public static
List
asList(T... a) { return new ArrayList<>(a); }
此时的ArrayList为Arrays里面自定义的一个私有的内部类
private static class ArrayList
extends AbstractList
implements RandomAccess, java.io.Serializable
其父类AbstractList中事务方法都被禁止了,使用时需要确保返回的list不会去修改。若需要修改可以修改为
new ArrayList<>(Arrays.asList(T... a));
public E set(int index, E element) { throw new UnsupportedOperationException(); } / * {@inheritDoc} * * 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} * *
This implementation always throws an * {@code UnsupportedOperationException}. * * @throws UnsupportedOperationException {@inheritDoc} * @throws IndexOutOfBoundsException {@inheritDoc} */ public E remove(int index) { throw new UnsupportedOperationException(); }
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