线程“main”中的异常 java.lang.ClassCastException: [我无法转换为 java.lang.Integer
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Exception in thread "main" java.lang.ClassCastException: [I cannot be cast to java.lang.Integer
提问by Ashish Patil
List<Integer> P = new ArrayList(Arrays.asList(p)); // Copies array p into Arraylist P
P.sort(null);
List<Integer> kk = new ArrayList();
kk.set(0, P.get(0)+k); //Exception generated on this line
I do not know why I'm unable to set it that way. Can anyone please help me on this? Thanks.
我不知道为什么我不能这样设置。任何人都可以帮我解决这个问题吗？谢谢。
回答by Eran
If pis a primitive array int[], Arrays.asList(p)would return a List whose single element is an int[]. That would explain why P.get(0)can't be cast to an Integer.
如果p是原始数组int[]，Arrays.asList(p)将返回一个列表，其单个元素是int[]。这将解释为什么P.get(0)不能转换为整数。
Change pto Integer[], and Arrays.asList()would generate the List you desire.
更改p为Integer[]，Arrays.asList()将生成您想要的列表。
It would also allow you to change this line :
它还允许您更改此行：
List<Integer> P = new ArrayList(Arrays.asList(p));
to
到
List<Integer> P = Arrays.asList(p);
You should avoid assigning a raw type to a generic type. This way you'd get a compilation error instead of a runtime error when you assign a List of the wrong type to P(which is easier to find and fix).
您应该避免将原始类型分配给泛型类型。这样，当您将错误类型的 List 分配给P（更容易查找和修复）时，您会收到编译错误而不是运行时错误。
