先说结论：
- 基元类型数组不允许协变和逆变，无法编译通过。
- 引用类型数组允许协变和逆变，逆变时会检查实际类型，如果不相符则抛出java.lang.ClassCastException。
下面是验证代码。
1 public class TestArrayInstance {
2 public static void main(
3 String[] args
4 ) {
5 char[] a1 = {'1', '2', '3'};
6 int[] a2 = {1, 2, 3};
7 long[] a3 = {1L, 2L, 3L};
8 float[] a4 = {1.0F, 2.0F, 3.0F};
9 double[] a5 = {1.0, 2.0, 3.0};
10 Integer[] a6 = {1, 2, 3};
11 Long[] a7 = {1L, 2L, 3L};
12
13 String[] a8 = {"1", "2", "3"};
14 Object[] a9 = {"1", 2L, 3};
15
16 printCheck(a1, Character[].class);
17 printCheck(a1, Object[].class);
18 printCheck(a2, Integer[].class);
19 printCheck(a2, Object[].class);
20 printCheck(a2, Long[].class);
21 printCheck(a2, long[].class);
22 printCheck(a3, Long[].class);
23 printCheck(a3, double[].class);
24 printCheck(a4, Float[].class);
25 printCheck(a4, Double[].class);
26 printCheck(a4, double[].class);
27 printCheck(a5, Double[].class);
28 printCheck(a6, Long[].class);
29 printCheck(a6, int[].class);
30 printCheck(a6, long[].class);
31 printCheck(a7, Double[].class);
32 printCheck(a7, long[].class);
33 printCheck(a7, int[].class);
34 printCheck(a8, Object[].class);
35 printCheck(a9, String[].class);
36 }
37
38 private static void printCheck(
39 Object v,
40 Class<?> c
41 ) {
42 System.out.println(paddingClassName(v.getClass()) + " instanceof " + paddingClassName(c) + (c.isInstance(v) ? " true" : " false"));
43 }
44
45 private static String paddingClassName(
46 Class<?> c
47 ) {
48 return (c.getSimpleName() + " ").substring(0, 12);
49 }
50 }
执行结果：
char[] instanceof Character[] false
char[] instanceof Object[] false
int[] instanceof Integer[] false
int[] instanceof Object[] false
int[] instanceof Long[] false
int[] instanceof long[] false
long[] instanceof Long[] false
long[] instanceof double[] false
float[] instanceof Float[] false
float[] instanceof Double[] false
float[] instanceof double[] false
double[] instanceof Double[] false
Integer[] instanceof Long[] false
Integer[] instanceof int[] false
Integer[] instanceof long[] false
Long[] instanceof Double[] false
Long[] instanceof long[] false
Long[] instanceof int[] false
String[] instanceof Object[] true
Object[] instanceof String[] false
