Arrays.asList的入参不同-小知识点

看代码

public class TestArrays {
    public static void main(String[] args) {
        Character[] array = new Character[]{'h','e','l','l','o'};

        char[] charArray = new char[]{'h','e','l','l','o'};


        List<Character> list1 = Arrays.asList(array);
        list1.forEach(System.out::println);


        List<char[]> list2 = Arrays.asList(charArray);
        list2.forEach(System.out::println);
    }
}

预测以上代码的输出结果是啥？

结果：

h
e
l
l
o
hello

原因

先来看一下Arrays.asList的源码

/**
     * 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 {@link Collection#toArray}.  The returned list is
     * serializable and implements {@link RandomAccess}.
     *
     * <p>This method also provides a convenient way to create a fixed-size
     * list initialized to contain several elements:
     * <pre>
     *     List&lt;String&gt; stooges = Arrays.asList("Larry", "Moe", "Curly");
     * </pre>
     *
     * @param <T> the class of the objects in the array
     * @param a the array by which the list will be backed
     * @return a list view of the specified array
     */
    @SafeVarargs
    @SuppressWarnings("varargs")
    public static <T> List<T> asList(T... a) {
        return new ArrayList<>(a);
    }

看其中入参要求the class of the objects in the array，即在数组中的objects的class类型。

此时再来看上述的代码，其中Character[]的数组中的对象的class类型为Character，而char[]的数组本身就是一个对象，里面再没有class类型了，所以这个时候入参的T类型就是char[]。