List 报错 java.lang.UnsupportedOperationException

空话不多说，上代码

public class ArrayListTest {

    @Test
    public void testList() {
        List<Long> longList = new ArrayList<>();
        longList.add(1L);
        longList.add(2L);
        longList.add(3L);
        longList.add(4L);
        longList.forEach(System.out::println);

        System.out.println("----------------------------------");

        List<Long> longList2 = Arrays.asList(1L, 2L, 3L);
        longList2.add(4L);
        longList2.forEach(System.out::println);
    }

}public class ArrayListTest {

    @Test